Sample records for gallium alloys

  1. Structure of dental gallium alloys.

    PubMed

    Herø, H; Simensen, C J; Jørgensen, R B

    1996-07-01

    The interest in gallium alloys as a replacement for amalgam has increased in recent years due to the risk of environmental pollution from amalgam. Alloy powders with compositions close to those for alloys of amalgam are mixed with a liquid gallium alloy. The mix is condensed into a prepared cavity in much the same way as for amalgam. The aim of the present work was to study the structure of: (1) two commercial alloy powders containing mainly silver, tin and copper, and (2) the phases formed by mixing these powders with a liquid alloy of gallium, indium and tin. One of the alloy powders contained 9 wt% palladium. Cross-sections of cylindrical specimens made by these gallium mixes were investigated by scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Discrete grains of the following phases were found to be present in both gallium alloys: hexagonal Ag2Ga, tetragonal Cu(Pd)Ga2, cubic Ag9In4 and tetragonal beta-Sn. Indications of hexagonal or orthorhombic Ag2Sn were found in the remaining, unreacted alloy particles. In the palladium-containing alloy the X-ray reflections indicate a minor fraction of cubic Cu9Ga4 in addition to the Cu(Pd)Ga2 phase. Particles of beta-Sn are probably precipitated because Sn-Ga phases cannot be formed according to the binary phase diagram. PMID:8805980

  2. Optical microcharacterization of gallium nitride and indium gallium nitride alloys

    NASA Astrophysics Data System (ADS)

    Srinivasan, Sridhar

    Gallium Nitride (GaN) and its alloys are attractive candidate materials for light-emitting applications in the visible and ultraviolet regions of the electromagnetic spectrum. The wide direct bandgap of the III-nitrides makes them very efficient light-emitters and their short bond length makes them extremely robust and durable. During the last decade, there have been rapid strides in the development of these materials and several devices based on them have already been commercialized. However, there are many issues with these materials that remain to be solved. This dissertation focuses on two main issues: one, the properties of Indium Gallium Nitride (InGaN) and two, the effect of dislocations on material properties. InGaN alloys are very difficult to grow, and a principal effort in the research community today is to achieve growth of high-quality films with high indium compositions. In order to overcome the problems associated with the growth of InGaN, it is important to gain an understanding of the basic nature of the material. In this work, the microstructure and electronic properties of thick InGaN epilayers has been studied. This enables investigation of material properties free of quantum confinement effects. The electronic properties of InGaN were observed to strongly vary with indium composition. Dislocations in the underlying GaN layer act as nucleation sites for phase separation and have a significant effect on material properties. The dislocation density was also found to play an important role in determining the strain relaxation mechanism in InGaN epilayers. The effect of dislocations on materials properties is an interesting problem that is being studied in great detail. In this study, it was found that the electronic properties in epitaxial lateral overgrowth of GaN are strongly dependent on the growth direction and unrelated to dislocation density. The properties appeared to be determined by point defects whose incorporation depends on the growth surface. Luminescence characteristics were studied across threading dislocations in semi-insulating GaN and were found to be closely related to the electrostatic potential measured by electron holography. This work has investigated important materials issues in GaN and InGaN and has contributed in developing a basic understanding of these materials.

  3. Method for Plutonium-Gallium Separation by Anodic Dissolution of a Solid Plutonium-Gallium Alloy

    SciTech Connect

    Miller, William E.; Tomczuk, Zygmunt

    1998-12-08

    Purified plutonium and gallium are efficiently recovered from a solid plutonium-gallium (Pu-Ga) alloy by using an electrorefining process. The solid Pu-Ga alloy is the cell anode, preferably placed in a moving basket within the electrolyte. As the surface of the Pu-Ga anode is depleted in plutonium by the electrotransport of the plutonium to a cathode, the temperature of the electrolyte is sufficient to liquify the surface, preferably at about 500 C, resulting in a liquid anode layer substantially comprised of gallium. The gallium drips from the liquified surface and is collected below the anode within the electrochemical cell. The transported plutonium is collected on the cathode surface and is recovered.

  4. Fundamental studies of the metallurgical, electrical, and optical properties of gallium phosphide and gallium phosphide alloys

    NASA Technical Reports Server (NTRS)

    1972-01-01

    Abstracts, bibliographic data, oral presentations, and published papers on (1) Diffusion of Sulfur in Gallium Phosphide and Gallium Arsenide, and (2) Properties of Gallium Phosphide Schottky Barrier Rectifiers for Use at High Temperature are presented.

  5. Gallium

    SciTech Connect

    NONE

    1996-01-01

    Discovered in 1875 through a study of its spectral properties, gallium was the first element to be uncovered following the publication of Mendeleev`s Periodic Table. French chemist, P.E. Lecoq de Boisbaudran, named his element discovery in honor of his native country; gallium is derived from the Latin word for France-{open_quotes}Gallia.{close_quotes}. This paper describes the properties, sources, and market for gallium.

  6. Miniature spherical motor using iron-gallium alloy (Galfenol)

    NASA Astrophysics Data System (ADS)

    Ueno, Toshiyuki; Saito, Chihiro; Imaizumi, Nobuo; Higuchi, Toshiro

    2008-03-01

    We propose a miniature spherical motor using iron-gallium alloy (Galfenol). This motor consists of four rods of Galfenol with square cross-section, a wound coil, a permanent magnet, an iron yoke and a spherical rotor placed on the edge of the rods. The magnetomotive force of the magnet provides bias magnetostriction for the rods and an attractive force that maintains the rotor on the rods. When currents of 180 deg phase difference flow in pairs of opposing coils, a torque is exerted on the rotor is by pushing (expansion) and pulling (contraction) of the rods. Rotation about a single axis is realized by a sawtooth current, such that the rotor rotates with slow expansion and slips at the rapid contraction. The motor can be fabricated at small sizes and driven with a low voltage, suitable for application as a microactuator for rotating the camera and mirror in endoscopes.

  7. Magnetostrictive bending micro-actuator using iron gallium-alloy

    NASA Astrophysics Data System (ADS)

    Ueno, Toshiyuki; Higuchi, Toshiro

    2007-04-01

    We investigate a micro bending actuator based on unimorph, lamination of Galfenol (Iron-gallium alloy) and non-magnetic material. Galfenol C-shape yoke bonded with stainless plates (lamination) is wound coils, and is composed close magnetic loop with connected an iron plate. The magnetostriction in longitude direction is constrained by the stainless, thus, the laminations yield bending deformation with the current flowing. The advantage of the actuator is simple, compact and ease of assembling including winding coil, and high tolerance against bending, tensile and impact. We machined the yoke from a plate of 1mm thickness of polycrystalline Galfenol (Fe 81.4Ga 18.6 Research grade) using ultra high precision cutting technique. The prototype, thickness of 1mm and length of 10mm, was observed the displacement 13?m and 1st resonance at 1.6 kHz, and the high bending (tensile) tolerance withstanding suspended weight of 500g.

  8. Electron backscatter diffraction of plutonium-gallium alloys

    SciTech Connect

    Boehlert, C. J. (Carl J.); Zocco, T. G. (Thomas G.); Schulze, R. K. (Roland K.); Mitchell, J. N. (Jeremy N.); Pereyra, R. A. (Ramiro A.)

    2002-01-01

    At Los Alamos National Laboratory a recent experimental technique has been developed to characterize reactive metals, including plutonium arid cerium, using electron backscatter diffraction (EBSD). Microstructural characterization of plutonium and its alloys by EBSD had been previously elusive primarily because of the extreme toxicity and rapid surface oxidation rate associated with plutonium metal. The experimental techniques, which included ion-sputtering the metal surface using a scanning auger microprobe (SAM) followed by vacuum transfer of the sample from the SAM to the scanning electron microscope (SEM), used to obtain electron backscatter diffraction Kikuchi patterns (EBSPs) and orientation maps for plutonium-gallium alloys are described and the initial microstructural observations based on the analysis are discussed. Combining the SEM and EBSD observations, the phase transformation behavior between the {delta} and {var_epsilon} structures was explained. This demonstrated sample preparation and characterization technique is expected to be a powerful means to further understand phase transformation behavior, orientation relationships, and texlure in the complicated plutonium alloy systems.

  9. Galvanic corrosion and cytotoxic effects of amalgam and gallium alloys coupled to titanium.

    PubMed

    Bumgardner, J D; Johansson, B I

    1996-06-01

    The aim of this study was to examine and compare the galvanic corrosion of a conventional, a dispersed high-copper, and a palladium-enriched spherical high-copper amalgam and a gallium alloy coupled to titanium in saline and cell culture solutions, and to evaluate the effects of the couples on cultured cells. The potentials and charge transfers between amalgams and titanium were measured by electrochemical corrosion methods. Cytotoxicity of the couples, as indicated by the uptake of neutral red vital stain, was determined in 24-h direct contact human gingival fibroblast cell cultures. Results of this study indicated that before connecting the high-copper amalgams to titanium, the amalgams exhibited more positive potentials which resulted in initial negative charge transfers, i.e. corrosion of titanium. However, this initial corrosion appeared to cause titanium to passivate, and a shift in galvanic currents to positive charge transfers, i.e. corrosion of the amalgam samples. Lower galvanic currents were measured for the amalgam-titanium couples as compared to the gallium alloy-titanium couple. Coupling the conventional or the palladium-enriched high-copper amalgams to titanium did not significantly affect the uptake of neutral red as compared to cells not exposed to any test alloy. However, significant cytotoxic effects were observed when the dispersed-type high-copper amalgam and the gallium alloy were coupled to titanium. Even though the corrosion currents measured for these couples were less than gold alloys coupled to amalgam, these results suggest there is the potential for released galvanic corrosion products to become cytotoxic. These data warrant further investigations into the effects of coupling amalgam and gallium alloys to titanium in the oral environment. PMID:8831065

  10. Novel Capacitance Measurements in Copper Indium Gallium Diselenide Alloys: Final Subcontract Report, 1 July 1999--31 August 2003

    Microsoft Academic Search

    Johnson

    2004-01-01

    This subcontract report describes the University of Oregon's objectives to measure the electronic properties of the copper indium\\/gallium diselenide alloys using several well-developed capacitance techniques appropriate for probing materials with a continuous distribution of semiconducting gap electronic energy states. We applied a new synthetic method to the production of CIGS alloys, namely, the modulated elemental reactant method. To form CIGS

  11. Solid electrolyte cell studies of solid nickel-gallium alloys

    Microsoft Academic Search

    J. N. Pratt; J. M. Bird

    1993-01-01

    Reversible galvanic cells employing ZrO2-CaO solid electrolytes and either Pt\\/O2 (air) or Ni\\/NiO reference electrodes were used to measure thermodynamic properties of solid Ni-Ga alloys at temperatures\\u000a between 873 and 1100 K. Activities, partial Gibbs energies, and integral Gibbs energies, entropies, and enthalpies have been\\u000a obtained for the a (fcc) solid solution and for the intermediate phases—Ni3Ga, Ni5Ga3, Ni3Ga2, Ni13Ga9,

  12. Alloying and Structure of Ultrathin Gallium Films on the (111) and (110) Surfaces of Palladium

    PubMed Central

    2013-01-01

    Growth, thermal stability, and structure of ultrathin gallium films on Pd(111) and Pd(110) are investigated by low-energy ion scattering and low-energy electron diffraction. Common to both surface orientations are growth of disordered Ga films at coverages of a few monolayers (T = 150 K), onset of alloy formation at low temperatures (T ? 200 K), and formation of a metastable, mostly disordered 1:1 surface alloy at temperatures around 400–500 K. At higher temperatures a Ga surface fraction of ?0.3 is slightly stabilized on Pd(111), which we suggest to be related to the formation of Pd2Ga bulk-like films. While on Pd(110) only a Pd-up/Ga-down buckled surface was observed, an inversion of buckling was observed on Pd(111) upon heating. Similarities and differences to the related Zn/Pd system are discussed. PMID:24089625

  13. Further studies of the anodic dissolution in sodium chloride electrolyte of aluminium alloys containing tin and gallium

    Microsoft Academic Search

    Maria Nestoridi; Derek Pletcher; Julian A. Wharton; Robert J. K. Wood

    2009-01-01

    As part of a programme to develop a high power density, Al\\/air battery with a NaCl brine electrolyte, the high rate dissolution of an aluminium alloy containing tin and gallium was investigated in a small volume cell. The objective was to define the factors that limit aluminium dissolution in condition that mimic a high power density battery. In a cell

  14. Short-Range Wetting at Liquid Gallium-Bismuth Alloy Surfaces: X-ray measurements and Square-Gradient theory.

    E-print Network

    Pershan, Peter S.

    alloy gallium-bismuth (Ga-Bi) in the region where the bulk phase separates into Bi-rich and Ga of the Bi-rich, low-surface-tension phase along several paths in the bulk phase diagram. The wetting to be absent in this binary liquid-metal alloy. PACS numbers: 61.25.Mv, 61.30.Hn, 68.10.­m, 61.10.­i I

  15. Characterization and modeling of the magnetomechanical behavior of iron-gallium alloys

    NASA Astrophysics Data System (ADS)

    Atulasimha, Jayasimha

    Magnetostrictive Iron-Gallium alloys (Galfenol) demonstrate moderate magnetostriction (˜350 ppm) under very low magnetic fields (˜100 Oe), have very low hysteresis, high tensile strength (˜500 MPa), high Curie temperature (˜675°C), are in general machinable, ductile and corrosion resistant. Therefore, they hold great promise in active vibration control, actuation, stress and torque sensing in helicopters, aircrafts and automobiles. To facilitate design of magnetostrictive actuators and sensors using this material, as well as to aid in making it commercially viable, it is necessary to perform a comprehensive characterization and modeling of its magnetomechanical behavior. This dissertation addresses some of these issues, focusing primarily on quasi-static characterization and modeling of the magnetomechanical behavior of single-crystal FeGa alloys with varying gallium content and along different crystallographic directions, and studying the effect of texture on the magnetomechanical behavior of polycrystals. Additionally, improved testing and modeling paradigms for magnetostrictive materials are developed to contribute to a better understanding and prediction of actuation and sensing behavior of FeGa alloys. In particular, the actuation behavior (lambda-H and B-H curves) for 19, 24.7 and 29 at. % Ga <100> oriented single crystal FeGa samples are characterized and the strikingly different characteristics are simulated and explained using an energy based model. Actuation and sensing (B-sigma and ?-sigma curves) behavior of <100> oriented 19 at. % Ga and <110> oriented 18 at. % Ga single crystal samples are characterized. It is demonstrated that the sensing behavior can be predicted by the model, using parameters obtained from the actuation behavior. The actuation and sensing behavior of 18.4 at. % Ga polycrystalline FeGa sample is predicted from the volume fraction of grains close to the [100], [110], [210], [310], [111], [211] and [311] orientations (obtained from cross-section texture analysis). The predictions are benchmarked against experimental actuator and sensor characteristics of the polycrystalline sample.

  16. Ab initio study of gallium stabilized ?-plutonium alloys and hydrogen-vacancy complexes.

    PubMed

    Hernandez, Sarah C; Schwartz, Daniel S; Taylor, Christopher D; Ray, Asok K

    2014-06-11

    All-electron density functional theory was used to investigate ?-plutonium (?-Pu) alloyed with gallium (Ga) impurities at 3.125, 6.25, 9.375 atomic (at)% Ga concentrations. The results indicated that the lowest energy structure is anti-ferromagnetic, independent of the Ga concentration. At higher Ga concentrations (>3.125?at%), the position of the Ga atoms are separated by four nearest neighbor Pu-Pu shells. The results also showed that the lattice constant contracts with increasing Ga concentration, which is in agreement with experimental data. Furthermore with increasing Ga concentration, the face-centered-cubic structure becomes more stably coupled with increasing short-range disorder. The formation energies show that the alloying process is exothermic, with an energy range of -0.028 to -0.099?eV/atom. The analyses of the partial density of states indicated that the Pu-Ga interactions are dominated by Pu 6d and Ga 4p hybridizations, as well as Ga 4s-4p hybridizations. Finally, the computed formation energies for vacancy and hydrogen-vacancy complexes within the 3.125?at% Ga cell were 1.12?eV (endothermic) and -3.88?eV (exothermic), respectively. In addition, the hydrogen atom prefers to interact much more strongly to the Pu atom than the Ga atom in the hydrogen-vacancy complex. PMID:24832613

  17. Micromagnetostrictive vibrator using a U-shaped core of iron-gallium alloy (Galfenol)

    NASA Astrophysics Data System (ADS)

    Ueno, T.; Higuchi, T.; Saito, C.; Imaizumi, N.; Wun-Fogle, M.

    2008-04-01

    A micromagnetostrictive vibrator using a U-shaped core made of iron-gallium alloy (Galfenol) was investigated. The vibrator consists of a Galfenol core, with a 1mm2 cross section, a length of 5.8mm, and a 0.3mm separation between the prongs of the "U," driving coils, and an iron yoke to close the magnetic loop. The Galfenol vibrator is superior to the PZT type in its high mechanical strength, low drive voltage requirements, and wide temperature operating range, and compared to our previous cylindrical type vibrator has a simpler construction and higher bandwidth. A displacement of 1.2?m (220ppm) was verified for the prototype with a 5.8mm long Galfenol core; the high magnetostriction >200ppm is inherited from the stress-annealed Galfenol. The displacement was also maintained under a 21MPa tensile stress (1.5kg hanging weight). Incorporation of a Nd-B-Fe magnet into the magnetic circuit successfully shifted the operating point to the linear portion of the magnetostrictive curves. This biasing effect is useful in reducing the drive voltage.

  18. Effect of tungsten and gallium on the structure and magnetic and mechanical properties of Fe-Cr-Co alloys

    NASA Astrophysics Data System (ADS)

    Belozerov, E. V.; Uimin, M. A.; Ermakov, A. E.; Serikov, V. V.; Kleinerman, N. M.; Ivanova, G. V.

    2008-11-01

    Effects of the alloying additions of W and Ga, cold deformation, and regimes of heat treatment on the magnetic and mechanical properties of precipitation-hardening Fe-Cr-Co alloys have been investigated. It has been shown that the alloying with tungsten leads to a strengthening of the ? solid solution and an additional jumplike increase in strength after deformation and age hardening. The coercive force grows simultaneously with an increase in strength; the structure of the alloy in this case contains a large concentration of linear defects (dislocations), which indicates an important contribution of magnetoelastic energy to the formation of the high-coercivity state and of elastic strains to the increase in the strength properties. The character of fracture becomes brittle. The modifying of the alloy with gallium leads to an increase in plasticity due to the dispersion of the structure, formation of retained austenite in it, and formation of an interphase layer more uniform in composition. The character of fracture changes from brittle to brittle-ductile. A high-strength magnetically hard material has been obtained with H c = 90-125 A/cm, ? m = 120-130 G cm3/g, B r = 0.6-0.65 T, ?0.2 = 1300-1600 MPa, and ? = 2.0-4.6%.

  19. Magnetic and Structural Properties in Non-Stoichiometric Gallium Deficient Ni2MnGa1-x Heusler Alloys

    NASA Astrophysics Data System (ADS)

    Ferralli, Ian; Ruffino, Anthony; Pierce, Michael; Barton, Linda

    2015-03-01

    Magnetic data show that off-stoichiometric gallium deficient Heusler alloys of the form Ni2MnGa1-x have martensite transition temperatures that increase strongly with x, while their ferromagnetic Curie temperatures remain nearly unchanged. The martensite transition approaches room temperature for x = 0 . 13 . Within the tetragonal martensite phase, bulk magnetic properties depend strongly on stresses within the sample. These effects were investigated using post annealing, thermal cycling, and grinding. These treatments effect the bulk coercivity but do not move the transition temperatures. As the martensite forms, lattice elongations of > 3 % are observed using XRD. Domain properties are reported, for both structural grains and magnetic ones, within the martensite phase, from optical and MFM imaging.

  20. Study of uranium solubility in gallium-indium eutectic alloy by emf method

    NASA Astrophysics Data System (ADS)

    Volkovich, V. A.; Maltsev, D. S.; Yamshchikov, L. F.; Osipenko, A. G.; Raspopin, S. P.; Kormilitsyn, M. V.

    2013-02-01

    Activity, activity coefficients and solubility of uranium in Ga-In eutectic alloy as well as activity of uranium in U-Ga and U-In alloys were determined between 573 and 1073 K using electromotive force (emf) method.

  1. Excessive thermodynamic properties of praseodymium in a gallium-indium alloy

    NASA Astrophysics Data System (ADS)

    Mel'chakov, S. Yu.; Yamshchikov, L. F.; Ivanov, V. A.; Volkovich, V. A.; Osipenko, A. G.; Kormilitsyn, M. V.; Nagovitsyn, V. A.

    2013-08-01

    The equilibrium potentials of praseodymium-diluted homogeneous Pr-Ga-In alloys in a (Li-K-Cs)Cleut-based salt electrolyte were measured between 573-1073 K by the emf method. These potentials are used to calculate the activity coefficients of ?-praseodymium in liquid Ga-In eutectic alloys. PrIn3 alloy with well-known thermodynamic characteristics and without phase transitions in the temperature range 428-1483 K was employed as the reference electrode.

  2. Gallium and gallium arsenide

    SciTech Connect

    Kramer, D.

    1988-01-01

    As part of the Nation's growing concern with the competitiveness of U.S. firms in the world economy, especially with respect to advanced materials, the Bureau of Mines assessed the actual and potential recovery and manufacturing capabilities for gallium and gallium arsenide (GaAs). GaAs has advanced from a laboratory curiosity to a material with important high-tech applications within only the last few years, and although protected North American gallium supplies are currently considered adequate, consumption could grow to the point that this assessment would need reevaluation.

  3. Silver catalyzed gallium phosphide nanowires integrated on silicon and in situ Ag-alloying induced bandgap transition.

    PubMed

    Huang, Kangrong; Zhang, Zhang; Zhou, Qingwei; Liu, Liwei; Zhang, Xiaoyan; Kang, Mengyang; Zhao, Fuli; Lu, Xubing; Gao, Xingsen; Liu, Junming

    2015-06-26

    In this work, we demonstrate a silver catalyzed heteroepitaxial growth of gallium phosphide nanowires (GaP NWs) on silicon. The morphology and growth direction of GaP NWs on differently orientated Si substrates were investigated. From crystallographic analysis, we inferred that Ag from catalyst is incorporated into the GaP during the chemical beam epitaxy (CBE) process. Using the PL spectrum and time-resolved emission spectroscopy, the optical properties of Ag-catalyzed GaP NWs were greatly modified, with bandgap transitions in the blue range. The Raman characterizations further confirmed the Ag incorporation into GaP during the growth. From the bandgap calculations, it was deduced that Ag was substituted on the Ga site with bandgap broadening. The in situ Ag-alloying during the growth of Ag-catalyzed GaP NWs greatly modified the band structure of GaP, and could lead to further applications in optoelectronics for low-dimensional GaP-based nanomaterials. PMID:26044077

  4. Silver catalyzed gallium phosphide nanowires integrated on silicon and in situ Ag-alloying induced bandgap transition

    NASA Astrophysics Data System (ADS)

    Huang, Kangrong; Zhang, Zhang; Zhou, Qingwei; Liu, Liwei; Zhang, Xiaoyan; Kang, Mengyang; Zhao, Fuli; Lu, Xubing; Gao, Xingsen; Liu, Junming

    2015-06-01

    In this work, we demonstrate a silver catalyzed heteroepitaxial growth of gallium phosphide nanowires (GaP NWs) on silicon. The morphology and growth direction of GaP NWs on differently orientated Si substrates were investigated. From crystallographic analysis, we inferred that Ag from catalyst is incorporated into the GaP during the chemical beam epitaxy (CBE) process. Using the PL spectrum and time-resolved emission spectroscopy, the optical properties of Ag-catalyzed GaP NWs were greatly modified, with bandgap transitions in the blue range. The Raman characterizations further confirmed the Ag incorporation into GaP during the growth. From the bandgap calculations, it was deduced that Ag was substituted on the Ga site with bandgap broadening. The in situ Ag-alloying during the growth of Ag-catalyzed GaP NWs greatly modified the band structure of GaP, and could lead to further applications in optoelectronics for low-dimensional GaP-based nanomaterials.

  5. Hort-Range Wetting at Liquid Gallium-Bismuth Alloy Surfaces: X-ray Measurements and Square-Gradient Theory

    SciTech Connect

    Huber, P.; Shpyrko, O; Pershan, P; Ocko, B; DiMasi, E; Deutsch, M

    2009-01-01

    We present an x-ray reflectivity study of wetting at the free surface of the binary liquid metal alloy gallium-bismuth (Ga-Bi) in the region where the bulk phase separates into Bi-rich and Ga-rich liquid phases. The measurements reveal the evolution of the microscopic structure of the wetting films of the Bi-rich, low-surface-tension phase along several paths in the bulk phase diagram. The wetting of the Ga-rich bulk's surface by a Bi-rich wetting film, the thickness of which is limited by gravity to only 50 Angstroms, creates a Ga-rich/Bi-rich liquid/liquid interface close enough to the free surface to allow its detailed study by x rays. The structure of the interface is determined with Angstromsngstrem resolution, which allows the application of a mean-field square gradient model extended by the inclusion of capillary waves as the dominant thermal fluctuations. The sole free parameter of the gradient model, the influence parameter K, that characterizes the influence of concentration gradients on the interfacial excess energy, is determined from our measurements. This, in turn, allows a calculation of the liquid/liquid interfacial tension, and a separation of the intrinsic and capillary wave contributions to the interfacial structure. In spite of expected deviations from MF behavior, based on the upper critical dimensionality (Du = 3 ) of the bulk, we find that the capillary wave excitations only marginally affect the short-range complete wetting behavior. A critical wetting transition that is sensitive to thermal fluctuations appears to be absent in this binary liquid-metal alloy.

  6. Effect of hydrogen and magnetic field on the mechanical behavior of magnetostrictive iron-gallium alloys

    NASA Astrophysics Data System (ADS)

    Ramanathan, Meenakshisundaram

    Magnetostrictive Fe-Ga and other iron-based alloys are candidates for use in sensing, actuation and large-scale energy harvesting applications. Exposure to aqueous electrochemical environments is anticipated in some of these applications which could potentially introduce hydrogen into the alloy and cause severe ductility reduction due to hydrogen embrittlement. These alloys may also be simultaneously exposed to magnetic field. This study therefore examines the effect of hydrogen and magnetic field on the mechanical behavior of these alloys. This study could also provide an understanding of the relationship between hydrogen embrittlement and magnetoelastic behavior in these alloys. In this work, the effect of hydrogen and magnetic field on the fracture behavior of [100]-oriented Fe-17.5 at.% Ga alloy single crystals and polycrystalline Fe-15 at.% Ga alloy were examined. Three-point bend tests and tensile tests were used to study the fracture behavior. Tests were done in different conditions to understand the effect of hydrogen and magnetic field on the fracture behavior of these materials. Hydrogen loading was done by in-situ electrochemical charging and magnetic field was applied to the samples either by using Nd2Fe 14B permanent magnets or by using solenoid coils. Before doing the three-point bend test on the Fe-Ga single crystal samples, tests were done using high-strength AISI 4340 steel to optimize the testing procedures and parameters. In all cases, the samples tested with hydrogen charging show a drastic reduction in ductility and fracture stress values. In the case of [100]-oriented Fe-17.5 at.% Ga alloy single crystal samples tested with hydrogen charging, the presence of applied magnetic field increased the stress required for fracture and a corresponding increase in bending strain values. This is attributed to a decrease of the elastic modulus values on the application of magnetic field in this magnetostrictive alloy. The hydrogen embrittlement was characterized by a change in fracture surface from a ductile type fracture to a brittle cleavage type fracture. Acoustic emission signals collected during the test correspond to the fracture behavior.

  7. Impact ionization in aluminum-gallium-arsenic-antimony alloy avalanche photodiodes

    NASA Astrophysics Data System (ADS)

    Grzesik, Michael

    Avalanche photodiodes (APDs) were designed and fabricated to determine the impact ionization coefficients of electrons (alpha) and holes (beta) in AlxGa1-xAsySb1-y lattice matched to GaSb for three alloy compositions: (x = 0.40, y = 0.035), (x = 0.55, y = 0.045), and (x = 0. 65, y = 0.054). The impact ionization coefficients were calculated from photomultiplication measurements made on specially designed APDs which allowed for both pure electron and pure hole injection in the same device. Photo-multiplication measurements were made at temperatures ranging from 77 K to 300 K for all three alloys. A quasi-physical model with an explicit temperature dependence was used to express the impact ionization coefficients as a function of electric-field strength and temperature. For all three alloys, it was found that alpha < beta at any given temperature. In addition, the values of the impact ionization coefficients were found to decrease as the aluminum concentration of the AlGaAsSb alloy was increased. A value between 1.4 and 5.3 was found for beta/alpha, which is dependent on temperature, alloy composition, and electric-field strength.

  8. Impact ionization in aluminum-gallium-arsenic-antimony alloy avalanche photodiodes

    Microsoft Academic Search

    Michael Grzesik

    2009-01-01

    Avalanche photodiodes (APDs) were designed and fabricated to determine the impact ionization coefficients of electrons (alpha) and holes (beta) in AlxGa1-xAsySb1-y lattice matched to GaSb for three alloy compositions: (x = 0.40, y = 0.035), (x = 0.55, y = 0.045), and (x = 0. 65, y = 0.054). The impact ionization coefficients were calculated from photomultiplication measurements made on

  9. Measurement of field-dependence elastic modulus of iron-gallium alloy using tensile test

    SciTech Connect

    Yoo, Jin-Hyeong; Flatau, Alison B. [University of Maryland, College Park, Maryland 20742 (United States)

    2005-05-15

    An experimental approach is used to identify Galfenol material properties under dc magnetic bias fields. Dog-bone-shaped specimens of single crystal Fe{sub 100-x}Ga{sub x}, where 18.6{<=}x{<=}33.2, underwent tensile testing along two crystallographic axis orientations, [110] and [100]. Young's modulus and Poisson's ratio sensitivity to magnetic fields and stoichiometry are investigated. Data are presented that demonstrate the dependence of these properties on applied magnetic-field levels and provide a substantial assessment of the trends in material properties for performance of alloys of different stoichiometries under varied operating conditions.

  10. Gallium Safety in the Laboratory

    SciTech Connect

    Cadwallader, L.C.

    2003-05-07

    A university laboratory experiment for the US Department of Energy magnetic fusion research program required a simulant for liquid lithium. The simulant choices were narrowed to liquid gallium and galinstan (Ga-In-Sn) alloy. Safety information on liquid gallium and galinstan were compiled, and the choice was made to use galinstan. A laboratory safety walkthrough was performed in the fall of 2002 to support the galinstan experiment. The experiment has been operating successfully since early 2002.

  11. Gallium Safety in the Laboratory

    SciTech Connect

    Lee C. Cadwallader

    2003-06-01

    A university laboratory experiment for the US Department of Energy magnetic fusion research program required a simulant for liquid lithium. The simulant choices were narrowed to liquid gallium and galinstan (Ga-In-Sn) alloy. Safety information on liquid gallium and galinstan were compiled, and the choice was made to use galinstan. A laboratory safety walkthrough was performed in the fall of 2002 to support the galinstan experiment. The experiment has been operating successfully since early 2002.

  12. Structure and properties of dilute nitride gallium arsenic nitride alloy films

    NASA Astrophysics Data System (ADS)

    Reason, Matthew J.

    Dilute nitride semiconductor alloys are useful for a wide range of applications. A fundamental understanding of how various growth regimes affect the structural, optical and electronic properties is needed for further optimization of device performance. This thesis explores these issues in GaAsN. We investigated the temperature-dependent mechanisms of growth for GaAsN films. At low temperatures, limited adatom surface mobility leads to layer-by-layer growth. As the temperature increases, the interplay between adatom surface diffusivity and the step-edge diffusion barrier leads to the formation of "mounds". For sufficiently high temperatures, adatoms overcome the step-edge diffusion barrier, resulting in layer-by-layer growth once again. Using a combination of nuclear reaction analysis and Rutherford backscattering spectrometry, we observe significant composition-dependent incorporation of N into non-substitutional sites, presumably as either N-N or N-As split interstitials. The (2x1) reconstruction is identified as the surface structure which leads to the highest substitutional N incorporation, presumably due to the high number of group V sites per unit area available for N-As surface exchange. For coherently strained films, a comparison of stresses measured via in-situ wafer curvature measurements, with those determined from x-ray rocking curves is used to quantify composition-dependent elastic constant bowing parameters. For films with x>2.5%, we observe that stress relaxation occurs by a combination of elastic relaxation via island formation and plastic relaxation associated with the formation of stacking faults. Optical absorption measurements reveal a substitutional nitrogen composition-dependent band gap energy reduction, which is less significant than typical literature reports. However, when the data are corrected to account for the typical 20% incorporation of non-substitutional nitrogen, all measurements reveal a band gap reduction of ˜125 meV per 1% N. Thus, GaAsN band gap bowing is most significantly influenced by substitutional nitrogen and smaller than previously reported. For bulk-like films, the electron mobility is observed to decrease with increasing N, independent of the arsenic species employed during growth. For GaAsN/GaAs:Si superlattices, the interface quality and electron mobilities are improved by controlling the N plasma flux using a pneumatic gate valve. In the AlGaAs/GaAsN channel layers, N-induced neutral scattering sources are identified as the dominant source of carrier scattering.

  13. Surface reconstructions and morphology of indium gallium arsenide compound semiconductor alloys

    NASA Astrophysics Data System (ADS)

    Riposan, Alexandru

    Lattice-matched In0.53Ga0.47As/InP(001) and compressively strained In0.27Ga0.73As/GaAs(001) and In0.81Ga 0.19As/InP(001) compound semiconductor layers were grown by molecular beam epitaxy (MBE) and analyzed by in-situ scanning tunneling microscopy (STM) and ex-situ atomic force microscopy (AFM). Regular (4x3) and irregular (nx3) alloy reconstructions were observed at all compositions. In addition, the strained surfaces contain alpha2(2x4) and beta2(2x4) reconstructions at the lower and higher In compositions, respectively. New models were proposed for the (4x3) reconstruction, which are consistent with the experimental results and obey the electron counting rule. In these models, the (4x3) reconstruction is As-rich, but contains As-metal heterodimers, in addition to As dimers and metal dimers. These models can also be used to compose disordered (nx3) surfaces while still obeying the electron counting rule. The experiments suggest that the (2x4) reconstructions are favored by compressive misfit strain and are enriched in In compared with the (4x3)/(nx3) reconstructions. At moderate misfit strains and temperatures, the critical film thickness for three-dimensional (3D) growth is increased by increasing the As overpressure during film deposition. This effect provides an additional method to control the transition to 3D growth and has applications in device fabrication. Large 3D islands form during the annealing of planar pseudomorphic In 0.27Ga0.73As/GaAs films, and later disappear with continuing annealing. These islands are different from those formed during film deposition. The formation of these features is strain-driven, while their dissolution is triggered by In desorption. A step instability was also observed during annealing at this composition, consisting in the cusping of step edges and the formation of surface pits and step bunches. The driving force for this instability is likely the creation of new step line due to the compressive strain, through step undulation due to the large step separation. The nucleation of 3D pits during the growth of In0.27Ga 0.73As/GaAs compressively strained films is a localized phenomenon, occurring only in the proximity of 3D islands and at small island separation. The nucleation of pits in these regions was attributed to a reduced critical pit size, as a result of the overlapping strain fields of 3D islands and a reduced adatom density between islands.

  14. Effect of tungsten and gallium on the structure and magnetic and mechanical properties of Fe-Cr-Co alloys

    Microsoft Academic Search

    E. V. Belozerov; M. A. Uimin; A. E. Ermakov; V. V. Serikov; N. M. Kleinerman; G. V. Ivanova

    2008-01-01

    Effects of the alloying additions of W and Ga, cold deformation, and regimes of heat treatment on the magnetic and mechanical\\u000a properties of precipitation-hardening Fe-Cr-Co alloys have been investigated. It has been shown that the alloying with tungsten\\u000a leads to a strengthening of the ? solid solution and an additional jumplike increase in strength after deformation and age\\u000a hardening. The

  15. Gallium complexes and solvent extraction of gallium

    SciTech Connect

    Coleman, J.P.; Graham, C.R.; Monzyk, B.F.

    1988-05-03

    This patent describes a process for recovering gallium from aqueous solutions containing gallium which comprises contacting such a solution with an organic solvent containing at least 2% by weight of a water-insoluble N-organo hydroxamic acid having at least about 8 carbon atoms to extract gallium, and separating the gallium loaded organic solvent phase from the aqueous phase.

  16. Bismuth in gallium arsenide: Structural and electronic properties of GaAs{sub 1-x}Bi{sub x} alloys

    SciTech Connect

    Reshak, Ali Hussain, E-mail: maalidph@yahoo.co.uk [School of Complex Systems, FFWP-South Bohemia University, Nove Hrady 37333 (Czech Republic); School of Material Engineering, Malaysia University of Perlis, P.O Box 77, d/a Pejabat Pos Besar, 01007 Kangar, Perlis (Malaysia); Kamarudin, H. [School of Material Engineering, Malaysia University of Perlis, P.O Box 77, d/a Pejabat Pos Besar, 01007 Kangar, Perlis (Malaysia); Auluck, S. [National Physical Laboratory Dr. KS Krishnan Marg, New Delhi 110012 (India); Kityk, I.V. [Electrical Engineering Department, Technological University of Czestochowa, Al. Armii Krajowej 17/19, Czestochowa (Poland)

    2012-02-15

    The structural and electronic properties of cubic GaAs{sub 1-x}Bi{sub x} alloys with bismuth concentration 0.0, 0.25, 0.50, 0.75 and 1.0 are studied using the 'special quasi-random structures' (SQS) approach of Zunger along with the generalized gradient approximation (GGA) and the Engel-Vosko generalized gradient approximation (EV-GGA). The lattice constant, bulk modulus, derivative of bulk modulus and energy gap vary with bismuth concentration nonlinearly. The present calculations show that the band gap decreases substantially with increasing bismuth concentration and that spin-orbit coupling influences the nature of bonding at high Bi concentrations. - Graphical abstract: Bowing effect of spin-orbit split-off band values versus Bi content with and without spin-orbit coupling for GaAs{sub 1-x}Bi{sub x} (at x=0.25, 0.50 and 0.75). Calculations are done with GGA. Highlights: Black-Right-Pointing-Pointer Structural and electronic properties of GaAs{sub 1-x}Bi{sub x} alloys were studied. Black-Right-Pointing-Pointer We present results of lattice constant, energy gap, bulk modulus and derivative. Black-Right-Pointing-Pointer The band gap decreases substantially with increasing Bi concentration. Black-Right-Pointing-Pointer Calculations of the density of states and charge densities are also presented. Black-Right-Pointing-Pointer We have performed calculations without and with spin-orbit coupling.

  17. Compatibility of ITER candidate structural materials with static gallium

    Microsoft Academic Search

    P. R. Luebbers; W. F. Michaud; O. K. Chopra

    1993-01-01

    Tests were conducted on the compatibility of gallium with candidate structural materials for the International Thermonuclear Experimental Reactor, e.g., Type 316 SS, Inconel 625, and Nb-5 Mo-1 Zr alloy, as well as Armco iron, Nickel 270, and pure chromium. Type 316 stainless steel is least resistant to corrosion in static gallium and Nb-5 Mo-1 Zr alloy is most resistant. At

  18. Orthodontic silver brazing alloys.

    PubMed

    Brockhurst, P J; Pham, H L

    1989-10-01

    Orthodontic silver brazing alloys suffer from the presence of cadmium, excessive flow temperatures, and crevice corrosion on stainless steel. Seven alloys were examined. Two alloys contained cadmium. The lowest flow temperature observed was 629 degrees C for a cadmium alloy and 651 degrees C for two cadmium free alloys. Three alloys had corrosion resistance superior to the other solders. Addition of low melting temperature elements gallium and indium reduced flow temperature in some cases but produced brittleness in the brazing alloy. PMID:2576971

  19. Gallium fluoroarsenates.

    PubMed

    Marshall, Kayleigh L; Armstrong, Jennifer A; Weller, Mark T

    2015-07-01

    Six new phases in the gallium-fluoride-arsenate system have been synthesised hydrofluorothermally using a fluoride-rich medium and "HAsF6" (HF?:?AsF5) as a reactant. RbGaF3(H2AsO4), KGaF(H2AsO4) and [piperazine-H2]2[Ga2F8(HAsO4)]·H2O have one dimensional structures, [DABCO-H2]2[Ga4F7O2H(AsO4)2]·4H2O consists of two dimensionally connected polyhedral layers, while GaF(AsO3[OH,F])2 and (NH4)3Ga4F9(AsO4)2 both have three-dimensionally connected polyhedral frameworks. PMID:26095086

  20. Compatibility of ITER candidate materials with static gallium

    Microsoft Academic Search

    P. R. Luebbers; O. K. Chopra

    1995-01-01

    Corrosion tests have been conducted to determine the compatibility of gallium with candidate structural materials for the International Thermonuclear Experimental Reactor (ITER) first wall\\/blanket systems, e.g., Type 316 stainless steel (SS), Inconel 625, and Nb-5 Mo-1 Zr. The results indicate that Type 316 SS is least resistant to corrosion in static gallium and Nb-5 Mo-1 Zr alloy is most resistant.

  1. Magnetostriction and Magnetic Heterogeneities in Iron-Gallium

    Microsoft Academic Search

    M. Laver; C. Mudivarthi; J. R. Cullen; A. B. Flatau; W.-C. Chen; S. M. Watson; M. Wuttig

    2010-01-01

    Iron-gallium alloys Fe1-xGax exhibit an exceptional increase in magnetostriction with gallium content. We present small-angle neutron scattering investigations on a Fe0.81Ga0.19 single crystal. We uncover heterogeneities with an average spacing of 15 nm and with magnetizations distinct from the matrix. The moments in and around the heterogeneities are observed to reorient with an applied magnetic field or mechanical strain. We

  2. Magnetostriction and Magnetic Heterogeneities in Iron-Gallium

    Microsoft Academic Search

    M. Laver; C. Mudivarthi; J. R. Cullen; M. Wuttig; A. B. Flatau; W.-C. Chen; S. M. Watson

    2010-01-01

    Iron-gallium alloys Fe{sub 1-x}Gaâ exhibit an exceptional increase in magnetostriction with gallium content. We present small-angle neutron scattering investigations on a Fe{sub 0.81}Ga{sub 0.19} single crystal. We uncover heterogeneities with an average spacing of 15 nm and with magnetizations distinct from the matrix. The moments in and around the heterogeneities are observed to reorient with an applied magnetic field or

  3. Purification of gallium from bismuth and polonium by melting under synthetic slags

    Microsoft Academic Search

    L. Wali?; L. Rowi?ska; A. Nowicki

    1994-01-01

    A method for the purification of technical grade gallium from bismuth and polonium by melting under synthetic slags is proposed. The examination of the purification degrees of gallium from bismuth and polonium was carried out with the aid of radioactive tracers210Bi and210Po. In order to obtain a gallium-bismuth alloy a suitable apparatus was assembled. The conditions of melting were established.

  4. Gallium nitride optoelectronic devices

    NASA Technical Reports Server (NTRS)

    Chu, T. L.; Chu, S. S.

    1972-01-01

    The growth of bulk gallium nitride crystals was achieved by the ammonolysis of gallium monochloride. Gallium nitride single crystals up to 2.5 x 0.5 cm in size were produced. The crystals are suitable as substrates for the epitaxial growth of gallium nitride. The epitaxial growth of gallium nitride on sapphire substrates with main faces of (0001) and (1T02) orientations was achieved by the ammonolysis of gallium monochloride in a gas flow system. The grown layers had electron concentrations in the range of 1 to 3 x 10 to the 19th power/cu cm and Hall mobilities in the range of 50 to 100 sq cm/v/sec at room temperature.

  5. Thermodynamic properties of uranium in Ga-In based alloys

    NASA Astrophysics Data System (ADS)

    Volkovich, V. A.; Maltsev, D. S.; Yamshchikov, L. F.; Melchakov, S. Yu; Shchetinskiy, A. V.; Osipenko, A. G.; Kormilitsyn, M. V.

    2013-07-01

    Activity of uranium was determined in gallium, indium and gallium-indium eutectic (21.8 wt.% In) based alloys between 573 and 1073 K employing the electromotive force method. In two-phase U-Ga-In alloys, uranium forms the intermetallic compound UGa3. Activity coefficients and solubility of uranium in Ga-In eutectic were also determined in the same temperature range. Partial thermodynamic functions of ?-U in saturated alloys with gallium, indium and Ga-In eutectic were calculated.

  6. Reversible expansion of gallium-stabilized (delta)-plutonium

    SciTech Connect

    Wolfer, W G; Oudot, B; Baclet, N

    2006-02-27

    It is shown that the transient expansion of plutonium-gallium alloys observed both in the lattice parameter as well as in the dimension of a sample held at ambient temperature can be explained by assuming incipient precipitation of Pu{sub 3}Ga. However, this ordered {zeta}-phase is also subject to radiation-induced disordering. As a result, the gallium-stabilized {delta}-phase, being metastable at ambient temperature, is driven towards thermodynamic equilibrium by radiation-enhanced diffusion of gallium and at the same time reverted back to its metastable state by radiation-induced disordering. A steady state is reached in which only a modest fraction of the gallium present is arranged in ordered {zeta}-phase regions.

  7. Isoelectronic Traps in Gallium Phosphide

    NASA Astrophysics Data System (ADS)

    Christian, Theresa; Alberi, Kirstin; Beaton, Daniel; Fluegel, Brian; Mascarenhas, Angelo

    2015-03-01

    Isoelectronic substitutional dopants can result in strongly localized exciton traps within a host bandstructure such as gallium arsenide (GaAs) or gallium phosphide (GaP). These traps have received great attention for their role in the anomalous bandgap bowing of nitrogen or bismuth-doped GaAs, creating the dramatic bandgap tunability of these unusual dilute alloys. In the wider, indirect-bandgap host material GaP, these same isoelectronic dopants create bound states within the gap that can have very high radiative efficiency and a wealth of discrete spectral transitions illuminating the symmetry of the localized excitonic trap state. We will present a comparative study of nitrogen and bismuth isoelectronic traps in GaP. Research was supported by the U. S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division under contract DE-AC36-08GO28308 and by the Department of Energy Office of Science Graduate Fellowship Program (DOE SCGF), made possible in part by the American Recovery and Reinvestment Act of 2009, administered by ORISE-ORAU under contract no. DE-AC05-06OR23100.

  8. Gallium interactions with Zircaloy 

    E-print Network

    West, Michael Keith

    1998-01-01

    : Nuclear Engineering GALLIUM INTERACTIONS WITH ZIRCALOY A Thesis by MICHAEL KEITH WEST Submitted to Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Approved as to style and content by: Ron R.... Hart (Chair of Co ittee) Karl T. H g, (Me e Marvin L. Adams (Member) Alan E. Waltar (Head of Department) December 1998 Major Subject: Nuclear Engineering ABSTRACT Gallium Interactions with Zircaloy. (December 1998) Michael Keith West, B. S...

  9. Preventing Supercooling Of Gallium

    NASA Technical Reports Server (NTRS)

    Massucco, Arthur A.; Wenghoefer, Hans M.; Wilkins, Ronnie

    1994-01-01

    Principle of heterogeneous nucleation exploited to prevent gallium from supercooling, enabling its use as heat-storage material that crystallizes reproducibly at its freezing or melting temperature of 29 to 30 degrees C. In original intended application, gallium used as heat-storage material in gloves of space suits. Terrestrial application lies in preparation of freezing-temperature reference samples for laboratories. Principle of heterogeneous nucleation also exploited similarly in heat pipes filled with sodium.

  10. Interactions of Zircaloy Cladding with Gallium: Final Report

    SciTech Connect

    D.F. Wilson; E.T. Manneschmidt; J.F. King; J.P. Strizak; J.R. DiStefano

    1998-09-01

    The U.S. Department of Energy has established a dual-track approach to the disposition of plutonium arising from the dismantling of nuclear weapons. Both immobilization and reactor-based mixed-oxide (MOX) fuel technologies are being evaluated. The reactor-based MOX fuel option requires assessment of the potential impact of concentrations of gallium (on the order of 1 to 10 ppm), not present in conventional MOX fhel, on cladding material performance. Three previous repmts"3 identified several compatibility issues relating to the presence of gallium in MOX fuel and its possible reaction with fiel cladding. Gallium initially present in weapons-grade (WG) plutonium is largely removed during processing to produce MOX fhel. After blending the plutonium with uranium, only 1 to 10 ppm gallium is expected in the sintered MOX fuel. Gallium present as gallium oxide (G~OJ could be evolved as the suboxide (G~O). Migration of the evolved G~O and diffusion of gallium in the MOX matrix along thermal gradients could lead to locally higher concentrations of G~03. Thus, while an extremely low concentration of gallium in MOX fiel almost ensures a lack of significant interaction of gallium whh Zircaloy fhel cladding, there remains a small probability that corrosion effects will not be negligible. General corrosion in the form of surface alloying resulting from formation of intermetallic compounds between Zircaloy and gallium should be ma& limited and, therefore, superficial because of the expected low ratio of gallium to the surface area or volume of the Zircaloy cladding. Although the expected concentration of gallium is low and there is very limited volubility of gallium in zirconium, especially at temperatures below 700 "C,4 grain boundary penetration and liquid metal embrittlement (LME) are forms of localized corrosion that were also considered. One fuel system darnage mechanism, pellet clad interaction, has led to some failure of the Zircaloy cladding in light-water reactors (LWRS). This has been attributed to stresses in the cladding and one or more aggressive fission products. Stress corrosion cracking by iodines' 6 and LME by cadmium7>8 have been reported, and it is known that Zircaloy can be embrittled by some low-melting metals, (e.g., mercury).g LME is a form of environmentally induced embrittlement that can induce cracking or loss of ductility. LME requties wetting and a tensile stress, but it does not require corrosion penetration. Experimentally, it has been demonstrated that gallium can cause embrittlement of some alloys (e.g., aluminum) at low temperatures,'"' ] ] but experiments relative to LME of zirconium by gallium have been limited and inconclusive.*2 This report describes a series of tests designed to establish the effects of low levels of residual gallium in WG-MOX fhel on its compatibility with Zircaloy. In addition, to establish damage mechanisms it was important to understand types of cladding interactions and available stiety margins with respect to gallium concentration.

  11. Visible light electroluminescent diodes of indium-gallium phosphide

    NASA Technical Reports Server (NTRS)

    Clough, R.; Richman, D.; Tietjen, J.

    1970-01-01

    Vapor deposition and acceptor impurity diffusion techniques are used to prepare indium-gallium phosphide junctions. Certain problems in preparation are overcome by altering gas flow conditions and by increasing the concentration of phosphine in the gas. A general formula is given for the alloy's composition.

  12. Optical Properties and Electronic Structures of d- and F-Electron Metals and Alloys, Silver-Indium Nickel - GOLD-GALLIUM(2), PLATINUM-GALLIUM(2), - - Cobalt-Aluminum CERIUM-TIN(3), and LANTHANUM-TIN(3)

    NASA Astrophysics Data System (ADS)

    Kim, Kwang Joo

    1990-01-01

    Optical properties and electronic structures of disordered Ag_{1-x}In_ {x} (x = 0.0, 0.04, 0.08, 0.12) and Ni_{1-x}Cu_{x }(x = 0.0, 0.1, 0.3, 0.4) alloys and ordered AuGa_2, PtGa _2, beta^' -NiAl, beta^' -CoAl, CeSn_3, and LaSn_3 have been studied. The complex dielectric functions have been determined for Ag_{1-x}In _{x},Ni_{1-x}Cu_ {x},AuGa_2, and PtGa_2 in the 1.2-5.5 eV region and for CeSn_3 and LaSn_3 in the 1.5-4.5 eV region using spectroscopic ellipsometry. Self-consistent relativistic band calculations using the linearized-augmented -plane-wave method have been performed for AuGa _2, PtGa_2,beta^' -CoAl, CeSn_3, and LaSn_3 to interpret the experimental optical spectra. In Ag_{1-x}In_{x} , the intraband scattering rate increases with increasing In concentration in the low-energy region (<3.5 eV). As the In concentration increases, the onset energy of the L_3to L_sp{2}{'}( E_{F}) transitions, 4.03 eV for pure Ag, shifts to higher energies, while that of the L_sp{2}{'}(E _{F}) to L_1 transitions, 3.87 eV for pure Ag, shifts to lower energies. This is only partly attributable to the rise of the Fermi level E_{F} caused by an increase in the average number of electrons per atom due to the In solute and to the narrowing of the Ag 4d-bands. The L_1-band may also lower as In is added. In Ni_{1-x}Cu_ {x}, the 4.7-eV edge (from transitions between the s-d-hybridized bands well below E_ {F} and the s-p-like bands above E _{F}, e.g., X_1 to X_sp{4}{'} ) shifts to higher energies, while the 1.5-eV edge (from transitions between a p-like band below E _{F} and a d-band above E _{F}, e.g., L_sp {2}{'} to L_3) remains at the same energy as the Cu concentration increases. A structure grows in the (2-3)-eV region as Cu is added, and it is interpreted as being due to transitions between the localized Cu subbands. For AuGa_2 and PtGa _2, both compounds show interband absorption at low photon energies (<1.3 eV). The interband absorption for AuGa_2 is strong at about 2 eV while that for PtGa_2 shows a broad structure in the range 2.5-4.5 eV, with a shoulder at 3.3 eV. The observed interband features in the imaginary parts of the complex dielectric functions epsilon_2 can be interpreted in terms of band calculational results. For beta ^'-NiAl and CoAl all of the structures found in the optical spectra of both compounds involve states with some Ni/Co d-character in both the initial and the final states of the transitions. A self-energy correction for the excitation spectrum has been used for beta^' -CoAl to improve the agreement. The optical conductivities of CeSn_3 and LaSn _3 show structures due to interband absorption at about 2 and 3 eV, which are mostly due to transitions between band-like Ce/La d- and f-states. The larger strengths of the structures in CeSn_3 than in LaSn_3 may be due to the existence of more f-character near E_{F} in CeSn_3 than in LaSn _3.

  13. Transport properties of proton-irradiated gallium nitride-based two-dimensional electron-gas system

    Microsoft Academic Search

    François Gaudreau; Patrick Fournier; Cosmo Carlone; Shyam M. Khanna; Haipeng Tang; Jim Webb; Alain Houdayer

    2002-01-01

    A two-dimensional electron gas system (2DEG) is formed at the interface when a ternary alloy of aluminum gallium nitride is grown on gallium nitride. Very high carrier density can be achieved in these systems due to the strong piezoelectric and pyroelectric properties of the nitrides. The device was grown by molecular beam epitaxy and magnetron sputtering epitaxy. Through resistivity and

  14. Effect of oxidation on the Mechanical Properties of Liquid Gallium and Eutectic Gallium-Indium

    E-print Network

    Xu, Qin; Guo, Qiti; Jaeger, Heinrich; Brown, Eric

    2012-01-01

    Liquid metals exhibit remarkable mechanical properties, in particular large surface tension and low viscosity. However, these properties are greatly affected by oxidation when exposed to air. We measure the viscosity, surface tension, and contact angle of gallium (Ga) and a eutectic gallium-indium alloy (eGaIn) while controlling such oxidation by surrounding the metal with an acid bath of variable concentration. Rheometry measurements reveal a yield stress directly attributable to an oxide skin that obscures the intrinsic behavior of the liquid metals. We demonstrate how the intrinsic viscosity can be obtained with precision through a scaling technique that collapses low- and high-Reynolds number data. Measuring surface tension with a pendant drop method, we show that the oxide skin generates a surface stress that mimics surface tension and develop a simple model to relate this to the yield stress obtained from rheometry. We find that yield stress, surface tension, and contact angle all transition from solid-...

  15. Thermal Conductivity of Indium–Graphene and Indium-Gallium–Graphene Composites

    Microsoft Academic Search

    K. Jagannadham

    2011-01-01

    Samples of graphene composites with a matrix of indium or indium-gallium alloy were prepared in the form of foils using exfoliated\\u000a graphene dispersions. The thermal conductivity of the composite samples with different thicknesses was determined using the\\u000a three-omega method. Indium–graphene composite samples with a thickness of 430 ?m exhibited a twofold increase in thermal conductivity, whereas indium-gallium–graphene composite samples with a

  16. Compatibility of ITER candidate materials with static gallium

    SciTech Connect

    Luebbers, P.R.; Chopra, O.K. [Argonne National Lab., IL (United States). Energy Technology Div.

    1995-09-01

    Corrosion tests have been conducted to determine the compatibility of gallium with candidate structural materials for the International Thermonuclear Experimental Reactor (ITER) first wall/blanket systems, e.g., Type 316 stainless steel (SS), Inconel 625, and Nb-5 Mo-1 Zr. The results indicate that Type 316 SS is least resistant to corrosion in static gallium and Nb-5 Mo-1 Zr alloy is most resistant. At 400 C, corrosion rates for Type 316 SS, Inconel 625, and Nb-5 Mo-1 Zr alloy are {approx} 4.0, 0.5, and 0.03 mm/yr, respectively. Iron, nickel, and chromium react rapidly with gallium. Iron shows greater corrosion than nickel at 400 C ({ge} 88 and 18 mm/yr, respectively). The present study indicates that at temperatures up to 400 C, corrosion occurs primarily by dissolution and is accompanied by formation of metal/gallium intermetallic compounds. The growth of intermetallic compounds may control the overall rate of corrosion.

  17. Gallium phosphide energy converters

    Microsoft Academic Search

    P. E. Sims; L. C. Dinetta; M. A. Goetz

    1995-01-01

    Gallium phosphide (GaP) energy converters may be successfully deployed to provide new mission capabilities for spacecraft. Betavoltaic power supplies based on the conversion of tritium beta decay to electricity using GaP energy converters can supply long term low-level power with high reliability. High temperature solar cells, also based on GaP, can be used in inward-bound missions greatly reducing the need

  18. Gallium interactions with Zircaloy

    SciTech Connect

    Woods, A.L. [ed.; West, M.K. [Texas A and M Univ., College Station, TX (United States). Dept. of Nuclear Engineering

    1999-01-01

    This study focuses on the effects of gallium ion implantation into zircaloy cladding material to investigate the effects that gallium may have in a reactor. High fluence ion implantation of Ga ions was conducted on heated Zircaloy-4 in the range of 10{sup 16}--10{sup 18} Ga ions/cm2. Surface effects were studied using SEM and electron microprobe analysis. The depth profile of Ga in the Zircaloy was characterized with Rutherford backscattering and SIMS techniques. Results indicate that the Zirc-4 is little affected up to a fluence of 10{sup 17} Ga ions/cm{sup 2}. After implantation of 10{sup 18} Ga ions/cm{sup 2}, sub-grain features on the order of 2 {micro}m were observed which may be due to intermetallic compound formation between Ga and Zr. For the highest fluence implant, Ga content in the Zirc-4 reached a saturation value of between 30 and 40 atomic %; significant enhanced diffusion was observed but gallium was not seen to concentrate at grain boundaries.

  19. SUR LES DIAGRAMMES D'ALLIAGES DU GALLIUM I OU II AVEC L'TAIN, LE ZINC OU L'INDIUM

    E-print Network

    Boyer, Edmond

    gallium II. Abstract. 2014 The authors compare, at atmospheric pressure, the diagrams of the binary alloys and the diagrams of tin with GaI or II are similar ; on the other hand, zinc and indium give intermetallic], [2] que l'on peut obtenir, à partir du gallium liquide maintenu en surfusion, une phase solide

  20. Oxidative dissolution of gallium arsenide and separation of gallium from arsenic

    SciTech Connect

    Coleman, J.P.; Monzyk, B.F.

    1988-07-26

    The method of dissociating gallium arsenide into a gallium-containing component and an arsenic-containing component, is described which comprises contacting the gallium arsenide with an oxidizing agent and a liquid comprising hydroxamic acid to convert the gallium to a gallium-hydroxamic acid complex and to oxidize the arsenic to a positive valence state.

  1. Real-time in-situ chemical sensing in aluminum gallium nitride\\/gallium nitride metal-organic chemical vapor deposition processes for advanced process control

    Microsoft Academic Search

    Soon Cho

    2004-01-01

    Gallium nitride and its alloys promise to be key materials for future semiconductor devices aimed at high frequency, high power electronic applications. However, manufacturing for such high performance products is challenged by reproducibility and material quality constraints that are notably more stringent than those required for optoelectronic applications. To meet this challenge, in-situ mass spectrometry was implemented as a real-time

  2. Gallium phosphide energy converters

    NASA Technical Reports Server (NTRS)

    Sims, P. E.; DiNetta, Louis C.; DuganCavanagh, K.; Goetz, M. A.

    1996-01-01

    Betavoltaic power supplies based on gallium phosphide can supply long term low-level power with high reliability. Results are presented for GaP devices powered by Ni-63 and tritiarated phosphors. Leakage currents as low as 1.2 x 10(exp -17) A/cm(exp 2) have been measured and the temperature dependence of the reverse saturation current is found to have ideal behavior. A small demonstration system has been assembled that generates and stores enough electricity to light up an LED.

  3. Gallium Arsenide Domino Circuit

    NASA Technical Reports Server (NTRS)

    Yang, Long; Long, Stephen I.

    1990-01-01

    Advantages include reduced power and high speed. Experimental gallium arsenide field-effect-transistor (FET) domino circuit replicated in large numbers for use in dynamic-logic systems. Name of circuit denotes mode of operation, which logic signals propagate from each stage to next when successive stages operated at slightly staggered clock cycles, in manner reminiscent of dominoes falling in a row. Building block of domino circuit includes input, inverter, and level-shifting substages. Combinational logic executed in input substage. During low half of clock cycle, result of logic operation transmitted to following stage.

  4. Machining of iron-gallium for microactuator

    NASA Astrophysics Data System (ADS)

    Ueno, Toshiyuki; Summers, Eric; Higuchi, Toshiro

    2006-03-01

    We investigate the machining properties of Iron-Gallium alloy for microactuator. Iron-Gallium is ductile magnetostrictive material with moderate magnetostriction ranging from 100 to 300ppm. The microactuator of Fe-Ga is expected to have advantages of simple configuration, low voltage driving, high robustness against external force and high temperature environment, compared with that of PZT. Here the rod of Fe-Ga prepared by FSZM technique was machined to distributed pillars of 1mm square by milling process. The comparison of magnetostrictions of machined and non-machined parts by strain gage confirms the strains different in pillars are inherited from the grain distribution and the milling process does not significantly deteriorate the material properties. The measurement of displacements by LASER Doppler vibrometer supports the validity of strain measurement. The success of the fabrication of the distributed pillars of 0.7 and 0.5mm square exhibits the potential of the milling process for Fe-Ga with high aspect ratio suitable for practical micro applications.

  5. Electrochemical study of one-step electrodeposition of copper–indium–gallium alloys in acidic conditions as precursor layers for Cu(In,Ga)Se 2 thin film solar cells

    Microsoft Academic Search

    L. Ribeaucourt; G. Savidand; D. Lincot; E. Chassaing

    2011-01-01

    This paper investigates one step electrodeposition of copper indium gallium metallic precursor layers for preparing CuIn1?xGaxSe2 (CIGS) absorber layers in thin film solar cells (0?x?1). Electrodeposition was carried out in acidic aqueous solutions at about pH 2. At first partial single or binary electrodeposition systems Cu, In, Ga, Cu–Ga, Cu–In were investigated by cyclic voltammetry. Then ternary Cu–In–Ga electrodeposition system

  6. Potential effects of gallium on cladding materials

    Microsoft Academic Search

    D. F. Wilson; E. C. Beahm; T. M. Besmann; J. H. DeVan; J. R. DiStefano; U. Gat; S. R. Greene; P. L. Rittenhouse; B. A. Worley

    1997-01-01

    This paper identifies and examines issues concerning the incorporation of gallium in weapons derived plutonium in light water reactor (LWR) MOX fuels. Particular attention is given to the more likely effects of the gallium on the behavior of the cladding material. The chemistry of weapons grade (WG) MOX, including possible consequences of gallium within plutonium agglomerates, was assessed. Based on

  7. Gallium phosphide energy converters

    NASA Technical Reports Server (NTRS)

    Sims, P. E.; Dinetta, L. C.; Goetz, M. A.

    1995-01-01

    Gallium phosphide (GaP) energy converters may be successfully deployed to provide new mission capabilities for spacecraft. Betavoltaic power supplies based on the conversion of tritium beta decay to electricity using GaP energy converters can supply long term low-level power with high reliability. High temperature solar cells, also based on GaP, can be used in inward-bound missions greatly reducing the need for thermal dissipation. Results are presented for GaP direct conversion devices powered by Ni-63 and compared to the conversion of light emitted by tritiarated phosphors. Leakage currents as low as 1.2 x 10(exp -17) A/sq cm have been measured and the temperature dependence of the reverse saturation current is found to have ideal behavior. Temperature dependent IV, QE, R(sub sh), and V(sub oc) results are also presented. These data are used to predict the high-temperature solar cell and betacell performance of GaP devices and suggest appropriate applications for the deployment of this technology.

  8. Gallium phosphide energy converters

    NASA Astrophysics Data System (ADS)

    Sims, P. E.; Dinetta, L. C.; Goetz, M. A.

    1995-10-01

    Gallium phosphide (GaP) energy converters may be successfully deployed to provide new mission capabilities for spacecraft. Betavoltaic power supplies based on the conversion of tritium beta decay to electricity using GaP energy converters can supply long term low-level power with high reliability. High temperature solar cells, also based on GaP, can be used in inward-bound missions greatly reducing the need for thermal dissipation. Results are presented for GaP direct conversion devices powered by Ni-63 and compared to the conversion of light emitted by tritiarated phosphors. Leakage currents as low as 1.2 x 10(exp -17) A/sq cm have been measured and the temperature dependence of the reverse saturation current is found to have ideal behavior. Temperature dependent IV, QE, R(sub sh), and V(sub oc) results are also presented. These data are used to predict the high-temperature solar cell and betacell performance of GaP devices and suggest appropriate applications for the deployment of this technology.

  9. Gallium phosphide energy converters

    SciTech Connect

    Sims, P.E.; Dinetta, L.C.; Goetz, M.A.

    1995-10-01

    Gallium phosphide (GaP) energy converters may be successfully deployed to provide new mission capabilities for spacecraft. Betavoltaic power supplies based on the conversion of tritium beta decay to electricity using GaP energy converters can supply long term low-level power with high reliability. High temperature solar cells, also based on GaP, can be used in inward-bound missions greatly reducing the need for thermal dissipation. Results are presented for GaP direct conversion devices powered by Ni-63 and compared to the conversion of light emitted by tritiarated phosphors. Leakage currents as low as 1.2 x 10(exp {minus}17) A/sq cm have been measured and the temperature dependence of the reverse saturation current is found to have ideal behavior. Temperature dependent IV, QE, R(sub sh), and V(sub oc) results are also presented. These data are used to predict the high-temperature solar cell and betacell performance of GaP devices and suggest appropriate applications for the deployment of this technology.

  10. A FETISH for gallium arsenide

    SciTech Connect

    Barron, A.R. [Rice Univ., Houston, TX (United States)

    1996-12-31

    An overview of the development of a new dielectric material, cubic-GaS, from the synthesis of new organometallic compounds to the fabrication of a new class of gallium arsenide based transistor is presented as a representative example of the possibility that inorganic chemistry can directly effect the development of new semiconductor devices. The gallium sulfido compound [({sup t}Bu)GaS]{sub 4}, readily prepared from tri-tert-butyl gallium, may be used as a precursor for the growth of GaS thin films by metal organic chemical vapor deposition (MOCVD). Photoluminescence and electronic measurements indicate that this material provides a passivation coating for GaAs. Furthermore, the insulating properties of cubic-GaS make it suitable as the insulating gate layer in a new class of GaAs transistor: a field effect transistor with a sulfide heterojunction (FETISH).

  11. Renal amyloidosis. Evaluation by gallium imaging

    SciTech Connect

    Lee, V.W.; Skinner, M.; Cohen, A.S.; Ngai, S.; Peng, T.T.

    1986-09-01

    A study has been performed to evaluate the efficacy of gallium imaging in the detection of renal amyloidosis. Ten of the 11 patients who had biopsy-proven renal amyloidosis demonstrated marked uptake in both kidneys. One patient revealed moderate gallium uptake in his kidneys. None of the patients had underlying renal or extrarenal pathology other than amyloidosis, which could account for renal gallium uptake (renal infection, neoplasm, hepatic failure or frequent blood transfusions). Four patients also had extrarenal foci of abnormal gallium uptake, suggesting other sites of amyloid deposits. Our data strongly suggest that gallium imaging has a high sensitivity for detection of renal amyloidosis. Its specificity is enhanced significantly by careful review of the clinical history to exclude other known causes of renal gallium uptake. Potentially, gallium imaging may be used to monitor the progress of patients under experimental therapy.

  12. Potential effects of gallium on cladding materials

    SciTech Connect

    Wilson, D.F.; Beahm, E.C.; Besmann, T.M.; DeVan, J.H.; DiStefano, J.R.; Gat, U.; Greene, S.R.; Rittenhouse, P.L.; Worley, B.A.

    1997-10-01

    This paper identifies and examines issues concerning the incorporation of gallium in weapons derived plutonium in light water reactor (LWR) MOX fuels. Particular attention is given to the more likely effects of the gallium on the behavior of the cladding material. The chemistry of weapons grade (WG) MOX, including possible consequences of gallium within plutonium agglomerates, was assessed. Based on the calculated oxidation potentials of MOX fuel, the effect that gallium may have on reactions involving fission products and possible impact on cladding performance were postulated. Gallium transport mechanisms are discussed. With an understanding of oxidation potentials and assumptions of mechanisms for gallium transport, possible effects of gallium on corrosion of cladding were evaluated. Potential and unresolved issues and suggested research and development (R and D) required to provide missing information are presented.

  13. A study of the applicability of gallium arsenide and silicon carbide as aerospace sensor materials

    NASA Technical Reports Server (NTRS)

    Hurley, John S.

    1990-01-01

    Most of the piezoresistive sensors, to date, are made of silicon and germanium. Unfortunately, such materials are severly restricted in high temperature environments. By comparing the effects of temperature on the impurity concentrations and piezoresistive coefficients of silicon, gallium arsenide, and silicon carbide, it is being determined if gallium arsenide and silicon carbide are better suited materials for piezoresistive sensors in high temperature environments. The results show that the melting point for gallium arsenide prevents it from solely being used in high temperature situations, however, when used in the alloy Al(x)Ga(1-x)As, not only the advantage of the wider energy band gas is obtained, but also the higher desire melting temperature. Silicon carbide, with its wide energy band gap and higher melting temperature suggests promise as a high temperature piezoresistive sensor.

  14. P-type gallium nitride

    DOEpatents

    Rubin, M.; Newman, N.; Fu, T.; Ross, J.; Chan, J.

    1997-08-12

    Several methods have been found to make p-type gallium nitride. P-type gallium nitride has long been sought for electronic devices. N-type gallium nitride is readily available. Discovery of p-type gallium nitride and the methods for making it will enable its use in ultraviolet and blue light-emitting diodes and lasers. pGaN will further enable blue photocathode elements to be made. Molecular beam epitaxy on substrates held at the proper temperatures, assisted by a nitrogen beam of the proper energy produced several types of p-type GaN with hole concentrations of about 5{times}10{sup 11} /cm{sup 3} and hole mobilities of about 500 cm{sup 2} /V-sec, measured at 250 K. P-type GaN can be formed of unintentionally-doped material or can be doped with magnesium by diffusion, ion implantation, or co-evaporation. When applicable, the nitrogen can be substituted with other group III elements such as Al. 9 figs.

  15. Gallium scan in intracerebral sarcoidosis

    SciTech Connect

    Makhija, M.C.; Anayiotos, C.P.

    1981-07-01

    Sarcoidosis involving the nervous system probably occurs in about 4% of patients. The usefulness of brain scintigraphy in these cases has been suggested. In this case of cerebral sarcoid granuloma, gallium imaging demonstrated the lesion before treatment and showed disappearance of the lesion after corticosteroid treatment, which correlated with the patient's clinical improvement.

  16. 40 CFR 721.10391 - Copper gallium indium selenide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...2014-07-01 2014-07-01 false Copper gallium indium selenide. 721.10391...Chemical Substances § 721.10391 Copper gallium indium selenide. (a) Chemical...The chemical substance identified as copper gallium indium selenide (PMN...

  17. 40 CFR 721.10391 - Copper gallium indium selenide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...2012-07-01 2012-07-01 false Copper gallium indium selenide. 721.10391...Chemical Substances § 721.10391 Copper gallium indium selenide. (a) Chemical...The chemical substance identified as copper gallium indium selenide (PMN...

  18. 40 CFR 721.10391 - Copper gallium indium selenide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...2013-07-01 2013-07-01 false Copper gallium indium selenide. 721.10391...Chemical Substances § 721.10391 Copper gallium indium selenide. (a) Chemical...The chemical substance identified as copper gallium indium selenide (PMN...

  19. Gallium nitride electronics

    NASA Astrophysics Data System (ADS)

    Rajan, Siddharth; Jena, Debdeep

    2013-07-01

    In the past two decades, there has been increasing research and industrial activity in the area of gallium nitride (GaN) electronics, stimulated first by the successful demonstration of GaN LEDs. While the promise of wide band gap semiconductors for power electronics was recognized many years before this by one of the contributors to this issue (J Baliga), the success in the area of LEDs acted as a catalyst. It set the field of GaN electronics in motion, and today the technology is improving the performance of several applications including RF cell phone base stations and military radar. GaN could also play a very important role in reducing worldwide energy consumption by enabling high efficiency compact power converters operating at high voltages and lower frequencies. While GaN electronics is a rapidly evolving area with active research worldwide, this special issue provides an opportunity to capture some of the great advances that have been made in the last 15 years. The issue begins with a section on epitaxy and processing, followed by an overview of high-frequency HEMTs, which have been the most commercially successful application of III-nitride electronics to date. This is followed by review and research articles on power-switching transistors, which are currently of great interest to the III-nitride community. A section of this issue is devoted to the reliability of III-nitride devices, an area that is of increasing significance as the research focus has moved from not just high performance but also production-worthiness and long-term usage of these devices. Finally, a group of papers on new and relatively less studied ideas for III-nitride electronics, such as interband tunneling, heterojunction bipolar transistors, and high-temperature electronics is included. These areas point to new areas of research and technological innovation going beyond the state of the art into the future. We hope that the breadth and quality of articles in this issue will make it an excellent reference for newcomers and experienced researchers in this field for several years. We thank Alice Malhador at IOP Publishing for her constant encouragement and guidance in putting together this special issue on GaN electronics.

  20. Effect of stoichiometry on sensing behavior of iron-gallium

    NASA Astrophysics Data System (ADS)

    Atulasimha, Jayasimha; Flatau, Alison B.; Chopra, Inderjit; Kellogg, Rick A.

    2004-07-01

    Iron-Gallium alloys demonstrate moderate magnetostriction (~350 ppm) and saturation material induction (~1 T) under low magnetic fields (~400 Oe) as well as high tensile strength (~500 MPa) and limited dependence of magnetomechanical properties on temperatures between -20°C and 80°C, making them promising materials for sensing and actuation applications. However, the mechanical and magnetic properties of these materials vary significantly with the percentage of gallium, which motivates this study on the effect of stoichiometry on the behavior of Fe-Ga alloys. Major loop compressive tests (loading to 110 MPa and unloading, at magnetic fields ranging from 0 to 891 Oe) were performed on single crystal 19% Ga and 24% Ga samples with longitudinal axis in the [100] direction. The effect of % Ga on Young's modulus, saturation magnetization (Msat), ?E-effect and d*33 are discussed and explained. Furthermore, it was found that the magnetic field (H) through the sample changed with applied stress. A simple magnetic circuit analysis is developed in the latter part of the paper to model this effect. The ramification of both stoichiometry effects and variation in field on the design of Fe-Ga sensors is discussed.

  1. Measurement of arsenic and gallium content of gallium arsenide semiconductor waste streams by ICP-MS

    Microsoft Academic Search

    Keith W. Torrance; Helen E. Keenan; Andrew S. Hursthouse; David Stirling

    2010-01-01

    The chemistry of semiconductor wafer processing liquid waste, contaminated by heavy metals, was investigated to determine arsenic content. Arsenic and gallium concentrations were determined for waste slurries collected from gallium arsenide (GaAs) wafer processing at three industrial sources and compared to slurries prepared under laboratory conditions. The arsenic and gallium content of waste slurries was analyzed using inductively coupled plasma

  2. Delta-phase manganese gallium on gallium nitride: a magnetically tunable spintronic system

    E-print Network

    Delta-phase manganese gallium on gallium nitride: a magnetically tunable spintronic system Kangkang, University of Michigan, Ann Arbor, MI 48109, U.S.A. ABSTRACT Ferromagnetic delta-phase manganese gallium to their potential for novel spintronics applications such as spin light-emitting diodes[1] . Delta phase manganese

  3. Epitaxial Deposition Of Germanium Doped With Gallium

    NASA Technical Reports Server (NTRS)

    Huffman, James E.

    1994-01-01

    Epitaxial layers of germanium doped with gallium made by chemical vapor deposition. Method involves combination of techniques and materials used in chemical vapor deposition with GeH4 or GeCl4 as source of germanium and GaCl3 as source of gallium. Resulting epitaxial layers of germanium doped with gallium expected to be highly pure, with high crystalline quality. High-quality material useful in infrared sensors.

  4. Facile synthesis of gallium oxide hydroxide by ultrasonic irradiation of molten gallium in water.

    PubMed

    Kumar, Vijay Bhooshan; Gedanken, Aharon; Porat, Ze'ev

    2015-09-01

    This work describes the single-step synthesis of GaO(OH) by ultrasonic irradiation of molten gallium in warm water. The ultrasonic energy causes dispersion of the liquid gallium into micrometric spheres, as-well-as decomposition of some of the water into H and OH radicals. The OH radicals and the dissolved oxygen react on the surface of the gallium spheres to form crystallites of GaO(OH). These crystallites prevent the re-coalescence of the gallium spheres, and as the reaction proceeds all the gallium is converted into crystalline GaO(OH). PMID:25819681

  5. A continuum thermodynamics formulation for micro-magneto-mechanics with applications to ferromagnetic shape memory alloys

    E-print Network

    the evolution of the martensite-free strain are shown to be equivalent to a hyperelastic strain gradient theory and mechanical coupling. For example, in nickel­magnesium­gallium (NiMnGa) alloys applied magnetic fields can

  6. Electron transport in the III-V nitride alloys

    SciTech Connect

    Foutz, B.E.; O'Leary, S.K.; Shur, M.S.; Eastman, L.F.

    1999-07-01

    The authors study electron transport in the alloys of aluminum nitride and gallium nitride and alloys of indium nitride and gallium nitride. In particular, employing Monte Carlo simulations they determine the velocity-field characteristics associated with these alloys for various alloy compositions. They also determine the dependence of the low-field mobility on the alloy composition. They find that while the low-field mobility is a strong function of the alloy composition, the peak and saturation drift velocities exhibit a more mild dependence. Transient electron transport is also considered. They find that the velocity overshoot characteristic is a strong function of the alloy composition. The device implications of these results are discussed.

  7. NIM Realization of the Gallium Triple Point

    Microsoft Academic Search

    Yan Xiaoke; Qiu Ping; Duan Yuning; Qu Yongmei

    2003-01-01

    In the last three years (1999 to 2001), the gallium triple-point cell has been successfully developed, and much corresponding research has been carried out at the National Institute of Metrology (NIM), Beijing, China. This paper presents the cell design, apparatus and procedure for realizing the gallium triple point, and presents studies on the different freezing methods. The reproducibility is 0.03

  8. Decreased gallium uptake in acute hematogenous osteomyelitis

    SciTech Connect

    Ang, J.G.; Gelfand, M.J.

    1983-07-01

    Decreased radiopharmaceutical uptake was noted on both bone and gallium scans in the case of acute hematogenous osteomyelitis of the right ilium (acetabular roof). This combination of findings is probably rare. The mechanism of decreased gallium uptake is unknown, but may be related to decreased blood flow.

  9. Gallium Electromagnetic (GEM) Thrustor Concept and Design

    NASA Technical Reports Server (NTRS)

    Polzin, Kurt A.; Markusic, Thomas E.

    2006-01-01

    We describe the design of a new type of two-stage pulsed electromagnetic accelerator, the gallium electromagnetic (GEM) thruster. A schematic illustration of the GEM thruster concept is given in Fig. 1. In this concept, liquid gallium propellant is pumped into the first stage through a porous metal electrode using an electromagneticpump[l]. At a designated time, a pulsed discharge (approx.10-50 J) is initiated in the first stage, ablating the liquid gallium from the porous electrode surface and ejecting a dense thermal gallium plasma into the second state. The presence of the gallium plasma in the second stage serves to trigger the high-energy (approx.500 I), send-stage puke which provides the primary electromagnetic (j x B) acceleration.

  10. Growth and Characterization of Copper INDIUM(1-X) Gallium(x) SELENIUM(2) and Copper Indium SULFUR(2Y) SELENIUM(2-2Y) Semiconductor Alloys and Evaluation of Their Electrochemical Solar Cells in IODINE(3)ION/IODIDE-ELECTROLYTE

    NASA Astrophysics Data System (ADS)

    Abid, Bader

    1991-02-01

    Crystals of CuIn_{1-x}Ga_{x} Se_2 and CuInS_ {2y}Se_{ 2-2y} were grown from stochiometric melts, by the gradient freeze method for different values of x and y respectively. With few exceptions these crystals were of p-type conductivity. In order to obtain n-type material, crystal growth experiments were also performed using Se deficient melt compositions, hence creating Se vacancies and related defects which act as donors. In addition, zone levelling was performed on two of the CuGa _{x}In _{1-x}Se_2 alloys to obtain more homogeneous crystals than accessible by gradient freezing. The band gap shift for these alloy systems with composition was established by photo-reflectance studies. The following band gap vs composition relationships were found. eqalign{E_{g } (CuIn_{1-x}Ga_{x }Se_2)&= 1.028 + 0.65 X + 0.21 X (X-1)cr E_{g} (CuInS_{2y}Se_{2-2y })& = 1.028 + 0.51 Y + 0.14 Y (Y-1)cr}Typical values for the carrier concentration were in the range of 10 ^{16} - 10^{17} per cm^3 as determined by Hall effect measurements. Chemical analysis of these bulk crystals were performed using Inductively Coupled Plasma Spectroscopy (ICP). The results of this method were reproducible within +/-1%. X ray diffraction studies were used to establish a and c axis lattice parameters. Linear relationships were found for the composition dependence of the lattice parameters. Photoluminescense studies on these alloys indicate that for CuIn_{1-x}Ga _{x}Se _2, there exists a greater variety of defect states inside the band gap than for comparable CuInS _{2y}Se_ {2-2y}. Semiconductor electrodes for these alloys were made by using In-Hg as back contact. Three-electrode photoelectrochemical cells were utilized using the standard calomel reference electrode and C as counter electrode. n-type CuInS _{2y}Se_ {2-2y} and CuIn_ {1-x}Ga_{x}Se_2 were evaluated in I_sp{3}{-} /I^- electrolyte. I-V curves indicate significant improvement in the values of V _{o.c} and F.F from the reported values for comparable n-CuInSe_2 electrochemical cell in the same electrolyte. Two of the best cells from each system were evaluated under AM0 conditions. The conversion efficiencies were found to be 6.8% for CuIn_{.88}Ga _{.12}Se_2 and 8.62% for CuInS_{.365} Se_{1.635}. p -type CuInS_{.2}Se _{1.8} photocathodes were evaluated in V^{+2}/V^ {+3} (E_0 = -0.49 volts) and Cr^{+2} /Cr^{+3} (E _0 = -0.65 volts) redox electrolyte. An improvement in the I-V characteristic was observed upon using more negative values of the electrode potential by reducing the ratio of trivalent ions to divalent ions by reduction with Zn metal. The I-V characteristics of p -CuInS_{2y}Se _{2-2y} significantly improved, upon letting the semiconductor electrode immersed in the electrolyte for some time, suggesting favorable surface conditioning by either etching of the electrode in the electrolyte solution or formation of a passivating film on the semiconductor electrode surface.

  11. Clinical Applications of Gallium-68

    PubMed Central

    Banerjee, Sangeeta Ray; Pomper, Martin G.

    2013-01-01

    Gallium-68 is a positron-emitting radioisotope that is produced from a 68Ge/68Ga generator. As such it is conveniently used, decoupling radiopharmacies from the need for a cyclotron on site. Gallium-68-labeled peptides have been recognized as a new class of radiopharmaceuticals showing fast target localization and blood clearance. 68Ga-DOTATOC, 8Ga-DOTATATE, 68Ga-DOTANOC, are the most prominent radiopharmaceuticals currently in use for imaging and differentiating lesions of various somatostatin receptor subtypes, overexpressed in many neuroendocrine tumors. There has been a tremendous increase in the number of clinical studies with 68Ga over the past few years around the world, including within the United States. An estimated ~10,000 scans are being performed yearly in Europe at about 100 centers utilizing 68Ga-labeled somatostatin analogs within clinical trials. Two academic sites within the US have also begun to undertake human studies. This review will focus on the clinical experience of selected, well-established and recently applied 68Ga-labeled imaging agents used in nuclear medicine. PMID:23522791

  12. The solubility of hydrogen and deuterium in alloyed, unalloyed and impure plutonium metal

    SciTech Connect

    Richmond, Scott [Los Alamos National Laboratory; Bridgewater, Jon S [Los Alamos National Laboratory; Ward, John W [Los Alamos National Laboratory; Allen, Thomas A [Los Alamos National Laboratory

    2009-01-01

    Pressure-Composition-Temperature (PCT) data are presented for the plutonium-hydrogen (Pu-H) and plutonium-deuterium (Pu-D) systems in the solubility region up to terminal solubility (precipitation of PuH{sub 2}). The heats of solution for PuH{sub s} and PuD{sub s} are determined from PCT data in the ranges 350-625 C for gallium alloyed Pu and 400-575 C for unalloyed Pu. The solubility of high purity plutonium alloyed with 2 at.% gallium is compared to high purity unalloyed plutonium. Significant differences are found in hydrogen solubility for unalloyed Pu versus gallium alloyed Pu. Differences in hydrogen solubility due to an apparent phase change are observable in the alloyed and unalloyed solubilities. The effect of iron impurities on Pu-Ga alloyed Pu is shown via hydrogen solubility data as preventing complete homogenization.

  13. Modulated optical sensitivity with nanostructured gallium nitride

    NASA Astrophysics Data System (ADS)

    Wilkins, S. J.; Slomski, M. J.; Paskova, T.; Weyher, J. L.; Ivanisevic, A.

    2015-04-01

    Surface functionalization via etching of high aspect ratio gallium nitride (GaN) nanostructures provides a way to modulate the optical properties in addition to properties gained from unique topographical formations. In this study, planar layered (heteroepitaxy) and bulk free-standing gallium nitride were modified via a phosphonic acid (1H,1H,2H,2H-perfluorooctanephosphonic acid) assisted phosphoric acid etch in conjunction with an aqueous KOH + K2S2O8 formed gallium nitride nanostructured surface. Despite the high defect concentrations in the thin planar and nanostructured GaN layer, the nanostructured GaN sample produced improved photoluminescence intensities versus the high quality bulk free-standing gallium nitride. Subsequent treatments with additive and additive-free phosphoric etches provided a means of additional optical manipulation in the form of red-shifting the near-band-edge (NBE) emission of the nanostructured GaN sample and increasing the maximum NBE photoluminescence intensity.

  14. The thermal conductivity of liquid gallium

    Microsoft Academic Search

    M. J. Duggin

    1969-01-01

    Thermal conductivity measurements have been made on gallium over the range 360°K-590°K. Values of the Lorenz number are obtained for several temperatures and indicate that inelastic scattering occurs.

  15. Chemical and electronic characterization of copper indium gallium diselenide thin film solar cells and correlation of these characteristics to solar cell operation

    Microsoft Academic Search

    Michael Justin Hetzer

    2009-01-01

    This dissertation embodies solid state physics research to understand the basic physical mechanisms underlying the movement of charge inside solar cells, in particular, the high efficiency copper indium gallium diselenide (CIGS) solar cell. The fundamental physics of the operation of these complex polycrystalline alloys remains incompletely understood. CIGS based solar cells have obtained conversion efficiencies of nearly 20%. Solar cells

  16. JOURNAL DE PHYSIQUE Colloque C4, supplkment au no 5, Tome 35, Mai 1974,page C4-313 LORENZ NUMBER AND THERMAL CONDUCTIVITY OF LIQUID GALLIUM,

    E-print Network

    Paris-Sud XI, Université de

    (derived from separate measurements of the thermal and electrical conductivity) of the liquid metals AND THERMAL CONDUCTIVITY OF LIQUID GALLIUM, MERCURY AND MERCURY-INDIUM ALLOYS G. BUSCH, H.-J. GUNTHERODT, W value for the Lorenz number. The thermal conductivity has been calculated from the Lorenz number

  17. Au-free Ohmic Contacts to Gallium Nitride and Graphene 

    E-print Network

    Ravikirthi, Pradhyumna

    2014-08-10

    This work deals with Au-free contact metallization schemes for gallium nitride (GaN) and graphene semiconductors. Graphene and gallium nitride are promising materials that can potentially be integrated together in the near future for high frequency...

  18. Window structure for passivating solar cells based on gallium arsenide

    NASA Technical Reports Server (NTRS)

    Barnett, Allen M. (Inventor)

    1985-01-01

    Passivated gallium arsenide solar photovoltaic cells with high resistance to moisture and oxygen are provided by means of a gallium arsenide phosphide window graded through its thickness from arsenic rich to phosphorus rich.

  19. Speciation of scandium and gallium in soil.

    PubMed

    Po?edniok, Justyna

    2008-09-01

    A method for the speciation of scandium and gallium in soil has been developed. The sequential extraction scheme of Tessier et al. for heavy metals was examined for the scandium and gallium separation. The regents proposed by Tessier were used for the extraction, and only for the residual fraction the HClO4 was replaced with H2SO4. The optimum conditions for leaching scandium and gallium from the soil were chosen for each fraction. Very sensitive, spectrophotometric methods based on the mixed complexes of Sc(III) and Ga(III) with Chrome Azurol S and benzyldodecyldimethylammonium bromide were applied for the scandium and gallium determination after their separation by solvent extraction. 100% mesityl oxide and a 0.5M solution of 2-thenoyltrifluoroacetone in xylene were chosen for the extraction of scandium and butyl acetate was selected for gallium. Soil samples from two different regions of Poland were the object of this research. The content of scandium and gallium found in the individual fractions of Upper Silesia soil (industrial region) was [in microgg(-1)] Sc: I, 1.52; II, 0.53; III, 7.78; IV, 1.79; V, 0.20; Ga: I, 24.7; III, 29.2; IV, 35.4; V, 6.9. In Podlasie soil (agricultural region), the content of both elements was clearly lower. The total content of scandium and gallium in the five soil fractions was in good correlation with the total content of these elements in the soils found after HF-H2SO4 digestion. Analysis using the ICP-OES method gave comparable results. PMID:18653213

  20. The Role of the Gallium Scan in Primary Extranodal Lymphoma

    Microsoft Academic Search

    Raihan Hussain; David R. H. Christie; Val Gebski; Michael B. Barton; Simon M. Gruenewald

    The purpose of this study was to examine the factors influencing gallium scan positivity for patients with primary extranodal lym- phoma and to examine the role of the gallium scan in staging the disease and assessing response to initial treatment. Methods: Ninety-two patients with extranodal lymphoma who had a gallium scan were reviewed. The influences of tumor site, size, grade

  1. /sup 67/Gallium lung scans in progressive systemic sclerosis

    SciTech Connect

    Baron, M.; Feiglin, D.; Hyland, R.; Urowitz, M.B.; Shiff, B.

    1983-08-01

    /sup 67/Gallium lung scans were performed in 19 patients with progressive systemic sclerosis (scleroderma). Results were expressed quantitatively as the /sup 67/Gallium Uptake Index. The mean total pulmonary /sup 67/Gallium Uptake Index in patients was significantly higher than that in controls (41 versus 25), and 4 patients (21%) fell outside the normal range. There were no clinical or laboratory variables that correlated with the /sup 56/Gallium uptake. Increased pulmonary /sup 67/Gallium uptake in scleroderma may prove useful as an index of pulmonary disease activity.

  2. Interactions of gallium with zircaloy cladding 

    E-print Network

    Mitchell, Lee Josey

    1999-01-01

    likely explanation for this Ga loss is sputtering by the incident ion beam. The estimated concentrations of Ga and Zr based on the RBS results are listed in Table 2. Again, it appears that the gallium has diffused into interstitial positions within... of Ga with Zr at Oak Ridge National Laboratory [4] Based on RBS data of Figure 17, the calculated gallium fluence was 2. 3x10" Ga atoms/cm . Again, it appears that sputtering removed a significant amount of the surface material. 24 3000 2500? 2000...

  3. Radiation damage of gallium arsenide production cells

    NASA Technical Reports Server (NTRS)

    Mardesich, N.; Joslin, D.; Garlick, J.; Lillington, D.; Gillanders, M.; Cavicchi, B.; Scott-Monck, J.; Kachare, R.; Anspaugh, B.

    1987-01-01

    High efficiency liquid phase epitaxy (LPE) gallium arsenide cells were irradiated with 1 Mev electrons up to fluences of 1 times 10 to the 16th power cm-2. Measurements of spectral response and dark and illuminated I-V data were made at each fluence and then, using computer codes, the experimental data was fitted to gallium arsenide cell models. In this way it was possible to determine the extent of the damage, and hence damage coefficients in both the emitter and base of the cell.

  4. Gallium stabilization of ?-Pu : Density-functional calculations

    NASA Astrophysics Data System (ADS)

    Sadigh, Babak; Wolfer, Wilhelm G.

    2005-11-01

    The ? and ? phases of plutonium differ in density by 25%. When alloyed with small amounts of gallium, the two phases can be converted directly into each other by a martensitic transformation. It occurs at even lower temperatures as the Ga content is increased, resulting in what has been called the ? stabilization of plutonium. The physical nature of this stabilization has remained unclear, in part because the anomalously low density of the ? phase has been a mystery. In addition, the atomic size of Ga in these two phases of Pu is perplexing, as it varies by nearly a factor of 3. We show in this paper that the key to the secret behind many of these anomalies rather lies in the unusual geometry of the ?-Pu structure than in the exotic electronic structure of the ?-Pu phase. We demonstrate this through extensive density-functional theory calculations that turn out to provide a sufficiently accurate model for the structural chemistry of the Pu-Ga alloys. The Ga volumes and their heats of solution in the various Pu phases are predicted in good agreement with the experiments. Using the results of our supercell calculations in combination with novel geometric arguments, we succeed in explaining the double-C behavior of the martensitic transformation of Pu, as well as the volume collapse due to the tempering of the ?' phase. We propose that these phenomena are manifestations of the temperature-dependent kinetics of ordering in what we call the eighth martensite variant of Ga-containing ?-Pu . We also give an account of the microscopic origin of the anomalous variability of the atomic sizes of Ga in Pu. In so doing, we discover that the measured size of the solute arises from induced volume changes in surrounding Pu atoms. We show that this is necessary for a correct interpretation of the EXAFS measurements of Ga-stabilized ?-Pu . This new effect may also be significant in other alloy systems.

  5. Four Terminal Gallium Nitride MOSFETs

    NASA Astrophysics Data System (ADS)

    Veety, Matthew Thomas

    All reported gallium nitride (GaN) transistors to date have been three-terminal devices with source, drain, and gate electrodes. In the case of GaN MOSFETs, this leaves the bulk of the device at a floating potential which can impact device threshold voltage. In more traditional silicon-based MOSFET fabrication a bulk contact can be made on the back side of the silicon wafer. For GaN grown on sapphire substrates, however, this is not possible and an alternate, front-side bulk contact must be investigated. GaN is a III-V, wide band gap semiconductor that as promising material parameters for use in high frequency and high power applications. Possible applications are in the 1 to 10 GHz frequency band and power inverters for next generation grid solid state transformers and inverters. GaN has seen significant academic and commercial research for use in Heterojunction Field Effect Transistors (HFETs). These devices however are depletion-mode, meaning the device is considered "on" at zero gate bias. A MOSFET structure allows for enhancement mode operation, which is normally off. This mode is preferrable in high power applications as the device has lower off-state power consumption and is easier to implement in circuits. Proper surface passivation of seminconductor surface interface states is an important processing step for any device. Preliminary research on surface treatments using GaN wet etches and depletion-mode GaN devices utilizing this process are discussed. Devices pretreated with potassium pursulfate prior to gate dielectric deposition show significant device improvements. This process can be applied to any current GaN FET. Enhancement-mode GaN MOSFETs were fabricated on magnesium doped p-type Wurtzite gallium nitride grown by Metal Organic Chemical Vapor Deposition (MOCVD) on c-plane sapphire substrates. Devices utilized ion implant source and drain which was activated under NH3 overpressure in MOCVD. Also, devices were fabricated with a SiO2 gate dielectric and metal gate. Preliminary devices exhibited high GaN-oxide interface state density, Dit, on the order of 1013 cm-2· eV-1. Additional experiments and device fabrication was focused on improving device performance through optimization of the ion implantation activation anneal as well as incorporation of a bulk p-type ohmic contact and migration to a thicker, lower defect density, HVPE-grown template substrate. The first reported MOSFET on HVPE grown GaN substrates (templates) is reported with peak measured drain current of 1.05 mA/mm and a normalized transconductance of 57 muS/mm. Fabricated devices exhibited large (greater than 1 muA) source-to-drain junction leakage which is attributed to low activated doping density in the MOCVD-grown p-type bulk. MOSFETs fabricated on template substrates show more than twice the measured drain current as similar devices fabricated on traditional MOCVD GaN on sapphire substrates for the same bias conditions. Also, template MOSFETs have decreased gate leakage which allowed for a much greater range of operation. This performance increase is attributed to a more than doubled effective channel mobility on template GaN MOSFETs due to decreased crystal defect scattering when compared to a MOCVD-grown GaN-on-sapphire MOSFET. Fabricated MOSFETs also exhibit decreased interface state density with lower bound of 2.2x1011 cm-2·eV-1 when compared to prelimary MOSFETs. This decrease is associated with the use of a sacrificial oxide cap during source/drain activation. Suggested work for continued research is also presented which includes experiments to improve source/drain ion implantation profile, utilization of selective area growth for the active area, improved n- and p-type ohmic contact resistance and investigation of alternate oxides.

  6. Optical identification of the gallium vacancy in neutron-irradiated gallium arsenide

    Microsoft Academic Search

    Anouar Jorio; Aiguo Wang; Martin Parenteau; Cosmo Carlone; Nelson L. Rowell; Shyam M. Khanna

    1994-01-01

    Gallium arsenide grown by the metallorganic-chemical-vapor-deposition method was irradiated at room temperature with fast neutrons in the fluence range 1012 to 3×1015 cm-2 (1.00 MeV equivalent fluence in gallium arsenide). The effects of neutron irradiation were studied by photoluminescence (PL) spectroscopy in the energy range 0.5-1.55 eV. In the samples irradiated to 3×1013 cm-2 and higher fluences, we observe a

  7. Synchrotron X-Ray Fluorescence Microscopy of Gallium in Bladder Tissue following Gallium Maltolate Administration during Urinary Tract Infection

    PubMed Central

    Sampieri, Francesca; Chirino, Manuel; Hamilton, Don L.; Blyth, Robert I. R.; Sham, Tsun-Kong; Dowling, Patricia M.; Thompson, Julie

    2013-01-01

    A mouse model of cystitis caused by uropathogenic Escherichia coli was used to study the distribution of gallium in bladder tissue following oral administration of gallium maltolate during urinary tract infection. The median concentration of gallium in homogenized bladder tissue from infected mice was 1.93 ?g/g after daily administration of gallium maltolate for 5 days. Synchrotron X-ray fluorescence imaging and X-ray absorption spectroscopy of bladder sections confirmed that gallium arrived at the transitional epithelium, a potential site of uropathogenic E. coli infection. Gallium and iron were similarly but not identically distributed in the tissues, suggesting that at least some distribution mechanisms are not common between the two elements. The results of this study indicate that gallium maltolate may be a suitable candidate for further development as a novel antimicrobial therapy for urinary tract infections caused by uropathogenic E. coli. PMID:23877680

  8. Gallium Electromagnetic (GEM) Thruster Performance Measurements

    NASA Technical Reports Server (NTRS)

    Thomas, Robert E.; Burton, Rodney L.; Polzin, K. A.

    2009-01-01

    Discharge current, terminal voltage, and mass bit measurements are performed on a coaxial gallium electromagnetic thruster at discharge currents in the range of 7-23 kA. It is found that the mass bit varies quadratically with the discharge current which yields a constant exhaust velocity of 20 km/s. Increasing the electrode radius ratio of the thruster from to 2.6 to 3.4 increases the thruster efficiency from 21% to 30%. When operating with a central gallium anode, macroparticles are ejected at all energy levels tested. A central gallium cathode ejects macroparticles when the current density exceeds 3.7 10(exp 8) A/square m . A spatially and temporally broad spectroscopic survey in the 220-520 nm range is used to determine which species are present in the plasma. The spectra show that neutral, singly, and doubly ionized gallium species are present in the discharge, as well as annular electrode species at higher energy levels. Axial Langmuir triple probe measurements yield electron temperatures in the range of 0.8-3.8 eV and electron densities in the range of 8 x 10(exp )20 to 1.6 x 10(exp 21) m(exp -3) . Triple probe measurements suggest an exhaust plume with a divergence angle of 9 , and a completely doubly ionized plasma at the ablating thruster cathode.

  9. A Gallium Multiphase Equation of State

    NASA Astrophysics Data System (ADS)

    Crockett, Scott; Greeff, Carl

    2009-06-01

    A new SESAME multiphase gallium equation of state (EOS) has been developed. The equation of state includes two of the solid phases (Ga I, Ga III) and a fluid phase. The EOS includes consistent latent heat between the phases. We compare the results to the liquid Hugoniot data. We will also explore refreezing via isentropic release and compression.

  10. Gallium nitride junction field-effect transistor

    DOEpatents

    Zolper, J.C.; Shul, R.J.

    1999-02-02

    An ion implanted gallium-nitride (GaN) junction field-effect transistor (JFET) and method of making the same are disclosed. Also disclosed are various ion implants, both n- and p-type, together with or without phosphorus co-implantation, in selected III-V semiconductor materials. 19 figs.

  11. Thermodynamic binding constants for gallium transferrin

    SciTech Connect

    Harris, W.R.; Pecoraro, V.L.

    1983-01-18

    Gallium-67 is widely used as an imaging agent for tumors and inflammatory abscesses. It is well stablished that Ga/sup 3 +/ travels through the circulatory system bound to the serum iron transport protein transferrin and that this protein binding is an essential step in tumor localization. However, there have been conflicting reports on the magnitude of the gallium-transferrin binding constants. Therefore, thermodynamic binding constants for gallium complexation at the two specific metal binding sites of human serum transferrin at pH 7.4 and 5 mM NaHCO/sub 3/ have been determined by UV difference spectroscopy. The conditional constants calculated for 27 mM NaHCO/sub 3/ are log K/sub 1/* = 20.3 and log K/sub 2/* = 19.3. These results are discussed in relation to the thermodynamics of transferrin binding of Fe/sup 3 +/ and to previous reports on gallium binding. The strength of transferrin complexation is also compared to that of a series of low molecular weight ligands by using calculated pM values (pM = -log (Ga(H/sub 2/O)/sub 6/)) to express the effective binding strength at pH 7.4.

  12. A Gallium Multiphase Equation of State

    Microsoft Academic Search

    Scott D Crockett; Carl Greeff

    2009-01-01

    A new SESAME multiphase gallium equation of state (EOS) has been developed. The equation of state includes two of the solid phases (Ga I, Ga III) and a fluid phase. The EOS includes consistent latent heat between the phases. We compare the results to the liquid Hugoniot data. We will also explore refreezing via isentropic release and compression.

  13. A GALLIUM MULTIPHASE EQUATION OF STATE

    Microsoft Academic Search

    Scott D. Crockett; Carl W. Greeff

    2009-01-01

    A new SESAME multiphase Gallium equation of state (EOS) has been developed. It includes three of the solid phases (Ga I, Ga II, Ga III) and a fluid phase (liquid?gas). The EOS includes consistent latent heat between the phases. We compare the results to the liquid Hugoniot data. We also explore the possibility of re-freezing via dynamic means such as

  14. a Gallium Multiphase Equation of State

    Microsoft Academic Search

    Scott D. Crockett; Carl W. Greeff

    2009-01-01

    A new SESAME multiphase Gallium equation of state (EOS) has been developed. It includes three of the solid phases (Ga I, Ga II, Ga III) and a fluid phase (liquid\\/gas). The EOS includes consistent latent heat between the phases. We compare the results to the liquid Hugoniot data. We also explore the possibility of re-freezing via dynamic means such as

  15. Gallium nitride junction field-effect transistor

    DOEpatents

    Zolper, John C. (Albuquerque, NM); Shul, Randy J. (Albuquerque, NM)

    1999-01-01

    An all-ion implanted gallium-nitride (GaN) junction field-effect transistor (JFET) and method of making the same. Also disclosed are various ion implants, both n- and p-type, together with or without phosphorous co-implantation, in selected III-V semiconductor materials.

  16. Chemistry and Pharmacokinetics of Gallium Maltolate, a Compound With High Oral Gallium Bioavailability

    PubMed Central

    Tanner, Trevor; Godfrey, Claire; Noll, Bruce

    2000-01-01

    Gallium maltolate, tris(3-hydroxy-2-methyl-4H-pyran-4-onato)gallium (GaM), is an orally active gallium compound for therapeutic use. It is moderately soluble in water (10.7 ± 0.9 mg/mL at 25?C) with an octanol partition coefficient of 0.41±0.08. The molecule is electrically neutral in aqueous solution at neutral pH; a dilute aqueous solution (2.5 ×10?-5 M) showed little dissociation at pH 5.5-8.0. Single crystal X-ray diffraction analysis found the GaM molecule to consist of three maltolate ligands bidentately bound to a central gallium atom in a propeller-like arrangement, with one of the ligands disordered in two possible orientations. The compound is orthorhombic, space group Pbca, unit cell a = 16.675(3), b = 12.034(2), c = 18.435(2) Å at 158K. GaM was administered to healthy human volunteers at single doses of 100, 200, 300, and 500 mg (three subjects per dose). GaM was very well tolerated. Oral absorption of Ga into plasma was fairly rapid (absorption half life = 0.8-2.0h), with a central compartment excretion half life of 17-21h. Absorption appeared dose proportional over the dosage range studied. Estimated oral gallium bioavailability was approximately 25-57%, based on comparison with published data on intravenous gallium nitrate. Urinary Ga excretion following oral GaM administration was approximately 2% of the administered dose over 72h, in contrast to 49-94% urinary Ga excretion over 24h following i.v. gallium nitrate administration. We suggest that oral administration of GaM results in nearly all plasma gallium being bound to transferrin, whereas i.v. administration of gallium nitrate results in formation of considerable plasma gallate [Ga(OH)4?], which is rapidly excreted in the urine. These data support the continued investigation of GaM as an orally active therapeutic gallium compound. PMID:18475921

  17. Gallium 67 scintigraphy in glomerular disease

    SciTech Connect

    Bakir, A.A.; Lopez-Majano, V.; Levy, P.S.; Rhee, H.L.; Dunea, G.

    1988-12-01

    To evaluate the diagnostic usefulness of gallium 67 scintigraphy in glomerular disease, 45 patients with various glomerulopathies, excluding lupus nephritis and renal vasculitis, were studied. Persistent renal visualization 48 hours after the gallium injection, a positive scintigram, was graded as + (less than), ++ (equal to), and +++ (greater than) the hepatic uptake. Positive scintigrams were seen in ten of 16 cases of focal segmental glomerulosclerosis, six of 11 cases of proliferative glomerulonephritis, and one case of minimal change, and one of two cases of membranous nephropathy; also in three of six cases of sickle glomerulopathy, two cases of diabetic neuropathy, one of two cases of amyloidosis, and one case of mild chronic allograft rejection. The 25 patients with positive scans were younger than the 20 with negative scans (31 +/- 12 v 42 +/- 17 years; P less than 0.01), and exhibited greater proteinuria (8.19 +/- 7.96 v 2.9 +/- 2.3 S/d; P less than 0.01) and lower serum creatinine values (2 +/- 2 v 4.1 +/- 2.8 mg/dL; P less than 0.01). The amount of proteinuria correlated directly with the intensity grade of the gallium image (P less than 0.02), but there was no correlation between the biopsy diagnosis and the outcome of the gallium scan. It was concluded that gallium scintigraphy is not useful in the differential diagnosis of the glomerular diseases under discussion. Younger patients with good renal function and heavy proteinuria are likely to have a positive renal scintigram regardless of the underlying glomerulopathy.

  18. Gallium nitride nanowire electromechanical resonators

    NASA Astrophysics Data System (ADS)

    Gray, Jason Michael

    Nanoscale mechanical resonators are of great interest for high-resolution sensing applications, where the small resonator mass and high quality factor (Q, defined as resonance frequency f0 over full width at half maximum power) lead to unprecedented sensitivity. Here, we investigate gallium nitride (GaN) nanowire (NW) resonators. The single-crystal, c-axis NWs are 5 mum -- 20 mum long, with diameters from 50 nm -- 500 nm, and grow essentially free of defects. Our initial experiments involve measuring the resonances of as-grown NWs in a scanning electron microscope, where we observe exceptionally high Q values of 10 4 -- 105, one to two orders of magnitude higher than most NWs of comparable size. Using a single NW as a mass sensor, we then demonstrate a sub-attogram mass sensitivity. To provide a more flexible measurement technique that avoids electron-microscope detection, we fabricate doubly clamped NWs with an entirely electronic drive and readout scheme using a combination of lithographic patterning and dielectrophoresis. An electrostatic gate induces vibration, while readout utilizes the piezoresistivity of GaN. Observed resonances range from 9--36 MHz with Q values typically around 103 at room temperature and 10 -4 Pa. We use the behavior of f0 and Q to sense the NW's local environment, such as the additional sources of energy dissipation not present in the as-grown NWs. By cooling the device to 8 K, Q increases by an order of magnitude to above 104, with a highest value to date of 26,000 under vacuum. We explore additional NW properties through the thermal noise in the NW's mechanical motion and the exponential decay of mechanical motion in the presence of burst drive. Finally, we investigate the low-frequency 1/f parameter noise displayed by f0. We show that the noise in f0 is consistent with noise in the NW's resistance leading to temperature noise from local Joule heating, which in turn generates resonance frequency noise. For sensor applications, there will be optimal drive conditions that balance the f 0 noise with the signal-to-noise ratio of the system. With these insights, along with the simple drive and readout technique, these GaN-NW doubly clamped resonators have significant potential for high-resolution sensing applications.

  19. Corrosion development between liquid gallium and four typical metal substrates used in chip cooling device

    NASA Astrophysics Data System (ADS)

    Deng, Yue-Guang; Liu, Jing

    2009-06-01

    The limitation of the currently available thermal management method has put an ever serious challenge for computer chip designers. A liquid metal with low melting point around room temperature was recently identified as a powerful coolant of driving heat away because of its superior thermo-physical properties and the unique ability to be driven efficiently by a completely silent electromagnetic pump. However, the adoption of gallium, one of the best candidates as metal coolant so far, may cause serious corrosion to the structure materials and subsequently affect the performance or even dangerous running of the cooling system. To address this emerging critical issue, here the compatibility of gallium with four typical metal substrates (6063 Aluminum-Alloy, T2 Copper-Alloy, Anodic Coloring 6063 Aluminum-Alloy and 1Cr18Ni9 Stainless Steel) was comprehensively investigated in order to better understand the corrosion mechanisms and help find out the most suitable structure material for making a liquid metal cooling device. To grasp in detail the dynamic corrosion behavior, an image acquisition and contrasting method was developed. Moreover, corrosion morphology analyses were performed by means of scanning electron microscope (SEM). The chemical compositions of the corroded layers were evaluated using energy dispersive spectrometry (EDS). According to the experiments, it was found that, the corrosion of the 6063 Aluminum-Alloy was rather evident and serious under the temperature range for chip cooling. The loose corrosion product will not only have no protection for the inner substrate, but also accelerate the corrosion process. Compared to the 6063 Aluminum-Alloy, T2 Copper-Alloy showed a slow and general corrosion, but part of the corrosion product can shed from the substrate, which will accelerate corrosion action and may block the flowing channel. Anodic Coloring 6063 Aluminum-Alloy and 1Cr18Ni9 Stainless Steel were found to have excellent corrosion resistance among these four specimens. No evident corrosion phenomena were found under the examination of SEM and EDS when exposed for 30 days at the temperature of 60°C, which suggests their suitability as structure materials for the flow of liquid metal. However, as for the Anodic Coloring 6063 Aluminum-Alloy, surface treatment and protection are of vital importance. The present study is of significance for making a liquid metal chip cooling device which can actually be used in the future computer industry.

  20. Recovery of nonwetting characteristics by surface modification of gallium-based liquid metal droplets using hydrochloric acid vapor.

    PubMed

    Kim, Daeyoung; Thissen, Peter; Viner, Gloria; Lee, Dong-Weon; Choi, Wonjae; Chabal, Yves J; Lee, Jeong-Bong J B

    2013-01-01

    The applicability of gallium-based liquid metal alloy has been limited by the oxidation problem. In this paper, we report a simple method to remove the oxide layer on the surface of such alloy to recover its nonwetting characteristics, using hydrochloric acid (HCl) vapor. Through the HCl vapor treatment, we successfully restored the nonwetting characteristics of the alloy and suppressed its viscoelasticity. We analyzed the change of surface chemistry before and after the HCl vapor treatment using X-ray photoelectron spectroscopy (XPS) and low-energy ion-scattering spectroscopy (LEIS). Results showed that the oxidized surface of the commercial gallium-based alloy Galinstan (Ga(2)O(3) and Ga(2)O) was replaced with InCl(3) and GaCl(3) after the treatment. Surface tension and static contact angle on a Teflon-coated glass of the HCl-vapor-treated Galinstan were measured to be 523.8 mN/m and 152.5°. A droplet bouncing test was successfully carried out to demonstrate the nonwetting characteristics of the HCl-vapor-treated Galinstan. Finally, the stability of the transformed surface of the HCl-vapor-treated Galinstan was investigated by measuring the contact angle and LEIS spectra after reoxidation in an ambient environment. PMID:23206334

  1. Interactions of zircaloy cladding with gallium -- 1997 status

    SciTech Connect

    Wilson, D.F.; DiStefano, J.R.; King, J.F.; Manneschmidt, E.T.; Strizak, J.P.

    1997-11-01

    A four phase program has been implemented to evaluate the effect of gallium in mixed oxide (MOX) fuel derived from weapons grade (WG) plutonium on Zircaloy cladding performance. The objective is to demonstrate that low levels of gallium will not compromise the performance of the MOX fuel system in LWR. This graded, four phase experimental program will evaluate the performance of prototypic Zircaloy cladding materials against: (1) liquid gallium (Phase 1), (2) various concentrations of Ga{sub 2}O{sub 3} (Phase 2), (3) centrally heated surrogate fuel pellets with expected levels of gallium (Phase 3), and (4) centrally heated prototypic MOX fuel pellets (Phase 4). This status report describes the results of an initial series of tests for phases 1 and 2. Three types of tests are being performed: (1) corrosion, (2) liquid metal embrittlement (LME), and (3) corrosion mechanical. These tests are designed to determine the corrosion mechanisms, thresholds for temperature and concentration of gallium that may delineate behavioral regimes, and changes in mechanical properties of Zircaloy. Initial results have generally been favorable for the use of WG-MOX fuel. The MOX fuel cladding, Zircaloy, does react with gallium to form intermetallic compounds at {ge} 300 C; however, this reaction is limited by the mass of gallium and is therefore not expected to be significant with a low level (in parts per million) of gallium in the MOX fuel. While continued migration of gallium into the initially formed intermetallic compound results in large stresses that can lead to distortion, this is also highly unlikely because of the low mass of gallium or gallium oxide present and expected clad temperatures below 400 C. Furthermore, no evidence for grain boundary penetration by gallium has been observed.

  2. Interactions of Zircaloy cladding with gallium: 1998 midyear status

    SciTech Connect

    Wilson, D.F.; DiStefano, J.R.; Strizak, J.P.; King, J.F.; Manneschmidt, E.T.

    1998-06-01

    A program has been implemented to evaluate the effect of gallium in mixed-oxide (MOX) fuel derived from weapons-grade (WG) plutonium on Zircaloy cladding performance. The objective is to demonstrate that low levels of gallium will not compromise the performance of the MOX fuel system in a light-water reactor. The graded, four-phase experimental program was designed to evaluate the performance of prototypic Zircaloy cladding materials against (1) liquid gallium (Phase 1), (2) various concentrations of Ga{sub 2}O{sub 3} (Phase 2), (3) centrally heated surrogate fuel pellets with expected levels of gallium (Phase 3), and (4) centrally heated prototypic MOX fuel pellets (Phase 4). This status report describes the results of a series of tests for Phases 1 and 2. Three types of tests are being performed: (1) corrosion, (2) liquid metal embrittlement, and (3) corrosion-mechanical. These tests will determine corrosion mechanisms, thresholds for temperature and concentration of gallium that may delineate behavioral regimes, and changes in the mechanical properties of Zircaloy. Initial results have generally been favorable for the use of WG-MOX fuel. The MOX fuel cladding, Zircaloy, does react with gallium to form intermetallic compounds at {ge}300 C; however, this reaction is limited by the mass of gallium and is therefore not expected to be significant with a low level (parts per million) of gallium in the MOX fuel. Although continued migration of gallium into the initially formed intermetallic compound can result in large stresses that may lead to distortion, this was shown to be extremely unlikely because of the low mass of gallium or gallium oxide present and expected clad temperatures below 400 C. Furthermore, no evidence for grain boundary penetration by gallium has been observed.

  3. The physics and modeling of gallium arsenide solar cells

    Microsoft Academic Search

    Paul David DeMoulin

    1988-01-01

    Gallium arsenide is a versatile semiconductor used in many devices. Due to its nearly ideal bandgap energy for solar energy conversion and its compatibility with AlGaAs, gallium arsenide's use in solar cells has been widespread and is growing. Only its chief rival, silicon, is more popular as a high-efficiency material. To continue gallium arsenide's growth, this research was conducted for

  4. Light Elements in the Core: Constraints from Gallium Partitioning

    NASA Astrophysics Data System (ADS)

    Blanchard, I.; Badro, J.; Siebert, J.; Ryerson, F. J.

    2014-12-01

    The formation of Earth's core has left a compositional imprint on the mantle, depleting and fractionating most of its siderophile (iron-loving) elements. Gallium is a moderately siderophile, hence it should be strongly depleted in the mantle. However, gallium concentration in the mantle matches that of lithophile (silicate-loving) elements having the same volatility. That is to say that either gallium behaves as a lithophile element during core formation, or a large influx of gallium was brought to the Earth after the core had formed. Geochemical evidence does not support the latter hypothesis, as it would require all other lithophile elements with similar volatility to be enriched in the mantle, or for late accretion to be composed of anomalously gallium-rich objects. In order to mitigate this issue, experimental studies have tried to understand how gallium behaves during core segregation by gauging the effects of pressure, temperature and oxygen fugacity on the partitioning of gallium between metal and silicate. None of these parameters provided the first-order change required to match the observation. We investigated the influence of core composition on gallium partitioning. The core in known to contain light-elements (oxygen, silicon sulfur and carbon), and those can change the activity of gallium in the metal, and strongly affect the behavior of gallium during core formation. We performed a series of metal-silicate partitioning experiments (2 GPa, 1673-2073 K) in a piston-cylinder press. We varied the light-element composition of the metal and observed that Si and O have a very strong influence on the activity of gallium, making it more lithophile. We then modeled terrestrial accretion as a continuous process and tested different accretion histories; we can reproduce the mantle concentration of gallium if the core segregates in a deep magma ocean (>40 GPa) and contains large amounts of silicon or oxygen.

  5. Inflammatory pseudotumor: A gallium-avid mobile mesenteric mass

    SciTech Connect

    Auringer, S.T.; Scott, M.D.; Sumner, T.E. (Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, NC (USA))

    1991-08-01

    An 8-yr-old boy with a 1-mo history of culture-negative fever and anemia underwent gallium, ultrasound, and computed tomography studies as part of the evaluation of a fever of unknown origin. These studies revealed a mobile gallium-avid solid abdominal mass subsequently proven to be an inflammatory pseudotumor of the mesentery, a rare benign mass. This report documents the gallium-avid nature of this rare lesion and discusses associated characteristic clinical, pathologic, and radiographic features.

  6. Optical properties and plasmonic response of silver-gallium nanostructures

    NASA Astrophysics Data System (ADS)

    Lereu, A. L.; Lemarchand, F.; Zerrad, M.; Yazdanpanah, M.; Passian, A.

    2015-02-01

    Silver and gallium form an alloy Ag2Ga via a room temperature spontaneous self-assembly that exhibits remarkable mechanical and electrical properties suitable for nanoscale measurements. However, whether photon excitation of plasmons in this emerging nanomaterial is retained or not has not been established. Here, we present a thin film formation of Ag2Ga via a spreading-reactive process of liquid Ga on an Ag film and a characterization of its dielectric function ?(E) = ?1(E) + i?2(E) in the photon energy range 1.42 eV ? E < 4.2 eV. It is observed that while the plasmon damping increases, near an energy of 2.25 eV, the real part of ? exhibits a crossing with respect to that of Ag. Furthermore, the impact of new plasmon supporting materials is discussed and in order to enable further applications in plasmonics, the possibility of photon excitation of surface plasmons in Ag2Ga is studied.

  7. Atomic gallium laser spectroscopy with violet/blue diode lasers

    E-print Network

    Marago, O M; Gucciardi, P G; Arimondo, E

    2003-01-01

    We describe the operation of two GaN-based diode lasers for the laser spectroscopy of gallium at 403 nm and 417 nm. Their use in an external cavity configuration enabled the investigation of absorption spectroscopy in a gallium hollow cathode. We have analyzed the Doppler broadened profiles accounting for hyperfine and isotope structure and extracting both the temperature and densities of the neutral atomic sample produced in the glow discharge. We have also built a setup to produce a thermal atomic beam of gallium. Using the GaN-based diode lasers we have studied the laser induced fluorescence and hyperfine resolved spectra of gallium.

  8. Determination of gallium originated from a gallium-based anticancer drug in human urine using ICP-MS

    Microsoft Academic Search

    Darya G. Filatova; Irina F. Seregina; Lidia S. Foteeva; Vladimir V. Pukhov; Andrei R. Timerbaev; Mikhail A. Bolshov

    2011-01-01

    Urine analysis gives an insight into the excretion of the administered drug which is related to its reactivity and toxicity.\\u000a In this work, the capability of inductively coupled plasma mass spectrometry (ICP-MS) to measure ultratrace metal levels was\\u000a utilized for rapid assaying of gallium originating from the novel gallium anticancer drug, tris(8-quinolinolato)gallium(III) (GaQ3), in human urine. Sample dilution with 1%

  9. A Gallium multiphase equation of state

    SciTech Connect

    Crockett, Scott D [Los Alamos National Laboratory; Greeff, Carl [Los Alamos National Laboratory

    2009-01-01

    A new SESAME multiphase Gallium equation of state (EOS) has been developed. The equation of state includes three of the solid phases (Ga I, Ga II, Ga III) and a fluid phase (liquid/gas). The EOS includes consistent latent heat between the phases. We compare the results to the liquid Hugoniol data. We also explore the possibility of re-freezing via dynamic means such as isentropic and shock compression.

  10. Wide Band Gap Gallium Phosphide Solar Cells

    Microsoft Academic Search

    Xuesong Lu; Susan Huang; Martin B. Diaz; Nicole Kotulak; Ruiying Hao; Robert Opila; Allen Barnett

    2012-01-01

    Gallium phosphide (GaP), with its wide band gap of 2.26 eV, is a good candidate for the top junction solar cell in a multijunction solar cell system. Here, we design, fabricate, characterize, and analyze GaP solar cells. Liquid phase epitaxy is used to grow the semiconductor layers. Four generations of GaP solar cells are developed and fabricated with each solar

  11. a Gallium Multiphase Equation of State

    NASA Astrophysics Data System (ADS)

    Crockett, Scott D.; Greeff, Carl W.

    2009-12-01

    A new SESAME multiphase Gallium equation of state (EOS) has been developed. It includes three of the solid phases (Ga I, Ga II, Ga III) and a fluid phase (liquid/gas). The EOS includes consistent latent heat between the phases. We compare the results to the liquid Hugoniot data. We also explore the possibility of re-freezing via dynamic means such as isentropic and shock compression. We predict an unusual spontaneous spreading of low pressure shocks from STP.

  12. Gallium Nitride Room Temperature ? Particle Detectors

    Microsoft Academic Search

    Lu Min; Zhang Guo-Guang; Fu Kai; Yu Guo-Hao

    2010-01-01

    Gallium Nitride (GaN) room temperature ? particle detectors are fabricated and characterized, whose device structure is Schottky diode. The current-voltage (I – V) measurements reveal that the reverse breakdown voltage of the detectors is more than 200 V owing to the consummate fabrication processes, and that the Schottky barrier and ideal factor of the detectors are 0.64 eV and 1.02,

  13. Gallium Nitride Room Temperature alpha Particle Detectors

    Microsoft Academic Search

    Min Lu; Guo-Guang Zhang; Kai Fu; Guo-Hao Yu

    2010-01-01

    Gallium Nitride (GaN) room temperature alpha particle detectors are fabricated and characterized, whose device structure is Schottky diode. The current-voltage (I - V) measurements reveal that the reverse breakdown voltage of the detectors is more than 200 V owing to the consummate fabrication processes, and that the Schottky barrier and ideal factor of the detectors are 0.64 eV and 1.02,

  14. Gallium Nitride Schottky betavoltaic nuclear batteries

    Microsoft Academic Search

    Min Lu; Guo-guang Zhang; Kai Fu; Guo-hao Yu; Dan Su; Ji-feng Hu

    2011-01-01

    Gallium Nitride (GaN) Schottky betavoltaic nuclear batteries (GNBB) are demonstrated in our work for the first time. GaN films are grown on sapphire substrates by metalorganic chemical vapor deposition (MOCVD), and then GaN Schottky diodes are fabricated by normal micro-fabrication process. Nickel with mass number of 63 (63Ni), which emits ? particles, is loaded on the GaN Schottky diodes to

  15. Anisotropic thermal expansion of copper gallium selenide

    Microsoft Academic Search

    P. Kistaiah; Y. C. Venudhar; K. Sathyanarayana Murthy; L. Iyengar; K. V. Krishna Rao

    1981-01-01

    Unit-cell parameters for the chalcopyrite type ternary semiconducting compound copper gallium selenide (CuGaSe2) have been determined accurately, using the least-squares method, for reflections in the range of Bragg angles 64-82 degrees , by the X-ray powder diffraction method. A study of the thermal expansion of the chalcopyrite structure unit-cell of the compound, determined over the temperature range 28-685 degrees C,

  16. Gallium-67 imaging in muscular sarcoidosis

    SciTech Connect

    Edan, G.; Bourguet, P.; Delaval, P.; Herry, J.Y.

    1984-07-01

    A case is presented of sarcoid myopathy in which radiogallium was seen to accumulate in the sites of muscle involvement. Uptake of the radiotracer disappeared following institution of corticosteroid therapy. The exceptional nature of this case contrasts with the high frequency of biopsy evidence of sarcoid granulomas in muscle. Gallium-67 imaging can be used to determine the extent of muscle involvement and, through evaluation of uptake intensity, the degree of disease activity before and after treatment.

  17. High-dose gallium imaging in lymphoma

    SciTech Connect

    Anderson, K.C.; Leonard, R.C.; Canellos, G.P.; Skarin, A.T.; Kaplan, W.D.

    1983-08-01

    The role of gallium-67 imaging in the management of patients with lymphoma, traditionally assessed using low tracer doses and the rectilinear scanner, was assessed when using larger doses (7 to 10 mCi) and a triple-peak Anger camera. Gallium scan results in 51 patients with non-Hodgkin's lymphoma and 21 patients with Hodgkin's disease were compared with simultaneous radiologic, clinical, and histopathologic reports. Subsequent disease course was also evaluated in light of radionuclide findings. Sensitivity and specificity of the scans were 0.90 or greater for both non-Hodgkin's lymphoma and Hodgkin's disease, and overall accuracy by site was 96 percent. Although there are insufficient numbers of pretreatment scans to allow any conclusions, our data suggest that newer approaches to gallium scanning in treated patients are (1) highly specific in all lymphomas and most sensitive in high-grade non-Hodgkin's lymphoma and Hodgkin's disease; (2) valuable in assessing the mediastinum in both non-Hodgkin's lymphoma and Hodgkin's disease; and (3) helpful adjuncts to computed tomographic scanning and ultrasonography in assessing abdominal node disease.

  18. Interactions of zircaloy cladding with gallium -- 1997 status

    Microsoft Academic Search

    D. F. Wilson; J. R. DiStefano; J. F. King; E. T. Manneschmidt; J. P. Strizak

    1997-01-01

    A four phase program has been implemented to evaluate the effect of gallium in mixed oxide (MOX) fuel derived from weapons grade (WG) plutonium on Zircaloy cladding performance. The objective is to demonstrate that low levels of gallium will not compromise the performance of the MOX fuel system in LWR. This graded, four phase experimental program will evaluate the performance

  19. Gallium scintigraphy in bone infarction. Correlation with bone imaging

    SciTech Connect

    Armas, R.R.; Goldsmith, S.J.

    1984-01-01

    The appearance of gallium-67 images in bone infarction was studied in nine patients with sickle cell disease and correlated with the bone scan findings. Gallium uptake in acute infarction was decreased or absent with a variable bone scan uptake, and normal in healing infarcts, which showed increased uptake on bone scan. The significance of these findings is discussed.

  20. Early Gallium-67 abdominal imaging: pitfalls due to bowel activity

    SciTech Connect

    Perkins, P.J.

    1981-05-01

    In gallium scanning for abdominal inflammatory disease, early imaging has been advocated so physiological activity within the bowel will not be confused with pathologic uptake. The normal physiologic pattern of bowel uptake is not desribed in the literature. Our study was undertaken to evaluate the frequency and patterns of gallium-67 bowel activity which may occur when early imaging is performed.

  1. Nuclear microprobe imaging of gallium nitrate in cancer cells

    NASA Astrophysics Data System (ADS)

    Ortega, Richard; Suda, Asami; Devès, Guillaume

    2003-09-01

    Gallium nitrate is used in clinical oncology as treatment for hypercalcemia and for cancer that has spread to the bone. Its mechanism of antitumor action has not been fully elucidated yet. The knowledge of the intracellular distribution of anticancer drugs is of particular interest in oncology to better understand their cellular pharmacology. In addition, most metal-based anticancer compounds interact with endogenous trace elements in cells, altering their metabolism. The purpose of this experiment was to examine, by use of nuclear microprobe analysis, the cellular distribution of gallium and endogenous trace elements within cancer cells exposed to gallium nitrate. In a majority of cellular analyses, gallium was found homogeneously distributed in cells following the distribution of carbon. In a smaller number of cells, however, gallium appeared concentrated together with P, Ca and Fe within round structures of about 2-5 ?m diameter located in the perinuclear region. These intracellular structures are typical of lysosomial material.

  2. Material and device properties of single-phase Cu(In,Ga)(Se,S) 2 alloys prepared by selenization\\/sulfurization of metallic alloys

    Microsoft Academic Search

    V. Alberts; J. Titus; R. W. Birkmire

    2004-01-01

    Single-phase Cu(In,Ga)(Se,S)2 alloys have been prepared using a novel two-step selenization\\/sulfurization growth process to react copper–indium–gallium alloy films. The growth scheme differs critically from standard two-step growth processes and is based on the manipulation of the reaction kinetics in order to inhibit the formation of stable ternary phases. In the first step, the metallic precursors are reacted with H2Se\\/Ar to

  3. The Preparation and Structural Characterization of Three Structural Types of Gallium Compounds Derived from Gallium (II) Chloride

    NASA Technical Reports Server (NTRS)

    Gordon, Edward M.; Hepp, Aloysius F.; Duraj. Stan A.; Habash, Tuhfeh S.; Fanwick, Phillip E.; Schupp, John D.; Eckles, William E.; Long, Shawn

    1997-01-01

    The three compounds Ga2Cl4(4-mepy)2 (1),[GaCl2(4-mepy)4]GaCl4x1/2(4-mepy); (2) and GaCl2(4-mepy)2(S2CNEt2); (3) (4-mepy= 4-methylpyridine) have been prepared from reactions of gallium (II) chloride in 4-methylpyridine and characterized by single-crystal X-ray analysis. Small variations in the reaction conditions for gallium(II) chloride can produce crystals with substantially different structural properties. The three compounds described here encompass a neutral gallium(II) dimer in which each gallium is four-coordinate, an ionic compound containing both anionic and cationic gallium complex ions with different coordination numbers and a neutral six-coordinate heteroleptic

  4. Resonant cavity modes in gallium oxide microwires

    NASA Astrophysics Data System (ADS)

    López, Iñaki; Nogales, Emilio; Méndez, Bianchi; Piqueras, Javier

    2012-06-01

    Fabry Perot resonant modes in the optical range 660-770 nm have been detected from single and coupled Cr doped gallium oxide microwires at room temperature. The luminescence is due to chromium ions and dominated by the broad band involving the 4T2-4A2 transition, strongly coupled to phonons, which could be of interest in tunable lasers. The confinement of the emitted photons leads to resonant modes detected at both ends of the wires. The separation wavelength between maxima follows the Fabry-Perot dependence on the wire length and the group refractive index for the Ga2O3 microwires.

  5. Distributed feedback gallium nitride nanowire lasers

    NASA Astrophysics Data System (ADS)

    Wright, Jeremy B.; Campione, Salvatore; Liu, Sheng; Martinez, Julio A.; Xu, Huiwen; Luk, Ting S.; Li, Qiming; Wang, George T.; Swartzentruber, Brian S.; Lester, Luke F.; Brener, Igal

    2014-01-01

    Achieving single-mode laser operation in nanowire lasers remains a challenge due to a lack of mode selection approaches. We have implemented single-mode lasing using distributed feedback by externally coupling gallium nitride nanowires to a dielectric grating to achieve mode-control. The effective periodicity of the grating experienced by the nanowire was altered using nanomanipulation to change the angular alignment between the nanowire and the grating. The effective periodicity controls the spectral location of the distributed feedback stop-band. Single-mode emission was achieved at an alignment, where the designed periodicity of the grating was experienced by the nanowire.

  6. Gallium-67 imaging in muscular sarcoidosis

    SciTech Connect

    Edan, G.; Bourguet, P.; Delaval, P.; Herry, J.Y.

    1984-07-01

    A case is presented of sarcoid myopathy in which radiogallium was seen to accumulate in the sites of muscle involvement. Uptake of the radiotracer disappeared following institution of corticosteroid therapy. The exceptional nature of this case contrasts with the high frequency of biopsy evidence of sarcoid muscle disease but is consistent with the rarity of clinical evidence of sarcoid granulomas in muscle. Gallium-67 imaging can be used to determine the extent of muscle involvement and, through evaluation of uptake intensity, the degree of disease activity before and after treatment.

  7. Behavior of Zircaloy Cladding in the Presence of Gallium

    SciTech Connect

    DiStefano, J.R.; King, J.F.; Manneschmidt, E.T.; Strizak, J.P.; Wilson, D.F.

    1998-09-28

    The U.S. Department of Energy has established a dual-track approach to the disposition of plutonium arising from the dismantling of nuclear weapons. Both immobilization and reactor-based mixed-oxide (MOX) fuel technologies are being evaluated. The reactor-based MOX fuel option requires assessment of the potential impact of concentrations of gallium (on the order of 1 to 10 ppm), not present in conventional MOX fuel, on cladding material performance. An experimental program was designed to evaluate the performance of prototypic Zircaloy cladding materials against (1) liquid gallium, and (2) various concentrations of G~03. Three types of tests were performed: (1) corrosion, (2) liquid metal embrittlement, and (3) corrosion-mechanical. These tests were to determine corrosion mechanisms, thresholds for temperature and concentration of gallium that delineate behavioral regimes, and changes in the mechanical properties of Zircaloy. Results have generally been favorable for the use of weapons-grade (WG) MOX fhel. The Zircaloy cladding does react with gallium to form intermetallic compounds at >3000 C; however, this reaction is limited by the mass of gallium and is therefore not expected to be significant with a low level (parts per million) of gallium in the MOX fuel. Furthermore, no evidence for grain boundary penetration by gallium or liquid metal embrittlement was observed.

  8. Doped gallium oxide nanowires for photonics

    NASA Astrophysics Data System (ADS)

    Nogales, E.; López, I.; Méndez, B.; Piqueras, J.; Lorenz, K.; Alves, E.; García, J. A.

    2012-02-01

    Monoclinic gallium oxide, ?-Ga2O3, is a transparent conducting oxide (TCO) that presents one of the widest band gaps among this family of materials. Its characteristics make it highly interesting for applications in UV - visible - IR optoelectronic and photonic devices. On the other hand, the morphology of nanowires made of this oxide presents specific advantages for light emitting nanodevices, waveguides and gas sensors. Control of doping of the nanostructures is of the utmost importance in order to tailor the behavior of these devices. In this work, the growth of the nanowires is based on the vapor-solid (VS) mechanism during thermal annealing treatment while the doping process was carried out in three different ways. In one of the cases, doping was obtained during the growth of the wires. A second method was based on thermal diffusion of the dopants after the growth of undoped nanowires, while the third method used ion implantation to introduce optically active ions into previously grown nanowires. The study of the influence of the different dopants on the luminescence properties of gallium oxide nanowires is presented. In particular, transition metals and rare earths such as Cr, Gd, Er or Eu were used as optically active dopants that allowed selection of the luminescence wavelength, spanning from the UV to the IR ranges. The benefits and drawbacks of the three different doping methods are analyzed. The waveguiding behavior of the doped nanowires has been studied by room temperature micro-photoluminescence.

  9. Characterization of semi-insulating gallium arsenide

    NASA Astrophysics Data System (ADS)

    Blakemore, John S.

    1991-08-01

    This project was established for the purpose of characterization of samples from melt grown single crystals of nominally undoped gallium arsenide, primarily such crystals as grown by the vertical zone melt (VZM) method at the Naval Research Laboratory. During this period electrical and optical samples were measured for 13 of these VZM-grown gallium arsenide. Measurements made at Western Washington University (WWU) under the terms of this project were in accordance with the Statement of Work provided at the project's outset: including near-infrared transmittance measurements for determination of neutral and ionized EL2 center concentrations, local vibrational mode (LVM) measurements in the mid-IR relative to carbon impurities, and measurements of dc electrical transport properties versus temperature. A program for growth of GaAs and other semiconductors by the VZM method began at NRL several years ago, and the practicality of this method for growing semi-insulating (SI) nominally undoped GaAs in a pBN crucible was demonstrated by Swiggard (1989) and in various subsequent papers.

  10. Measurement of the solar neutrino capture rate with gallium metal

    SciTech Connect

    SAGE Collaboration

    1999-11-01

    The solar neutrino capture rate measured by the Russian-American Gallium Experiment (SAGE) on metallic gallium during the period January 1990 through December 1997 is 67.2{sub {minus}7.0{minus}3.0}{sup +7.2+3.5} SNU, where the uncertainties are statistical and systematic, respectively. This represents only about half of the predicted standard solar model rate of 129 SNU. All the experimental procedures, including extraction of germanium from gallium, counting of {sup 71}Ge, and data analysis, are discussed in detail. {copyright} {ital 1999} {ital The American Physical Society}

  11. Microencapsulation of gallium-indium (Ga-In) liquid metal for self-healing applications.

    PubMed

    Blaiszik, B J; Jones, A R; Sottos, N R; White, S R

    2014-01-01

    Microcapsules containing a liquid metal alloy core of gallium-indium (Ga-In) are prepared via in situ urea-formaldehyde (UF) microencapsulation. The capsule size, shape, thermal properties, and shell wall thickness are investigated. We prepare ellipsoidal capsules with major and minor diameter aspect ratios ranging from 1.64 to 1.08 and with major diameters ranging from 245?µm to 3?µm. We observe that as the capsule major diameter decreases, the aspect ratio approaches 1. The thermal properties of the prepared microcapsules are investigated by thermogravimetric (TGA) and differential scanning calorimetry (DSC). Microcapsules are shown to survive incorporation into an epoxy matrix and to trigger via mechanical damage to the cured matrix. Microcapsules containing liquid metal cores may have diverse applications ranging from self-healing to contrast enhancement or the demonstration of mechano-adaptive circuitry. PMID:24495196

  12. Hyperfine Magnetic Field Measurements in the Heusler Alloys COBALT(2)-TITANIUM-Z, COBALT(2)-MAGNESIUM-Z (z = Silicon, Germanium, and Tin) and COBALT(2)-MAGNESIUM- Gallium Using the Moessbauer Effect (me) and the Time Differential Perturbed Angular Correlation (tdpac) Techniques

    NASA Astrophysics Data System (ADS)

    Lahamer, Amer Said

    1990-01-01

    Measurements of the hyperfine magnetic field in a series of Heusler alloys were performed. The probes were in (^{119}Sn) and cadmium (^{111}Cd). These measurements were performed at the University of Cincinnati in Cincinnati, Ohio. Two techniques were used. The first technique was the Mossbauer effect, which was used to measure the hyperfine magnetic field on ^{119 }Sn in Co_2TiZ (Z = Si, Ge, and Sn), and the second technique was the Time Differential Perturbed Angular Correlation which was used to measure the hyperfine magnetic field on ^ {111}Cd in the Co_2MnZ (Z = Si, Ge, Sn, and Ga). The probes are expected to go to the Z sites of the alloys. The hyperfine magnetic field measurements on ^{119}Sn in Co _2TiZ (Z = Si, Ge, and Sn) alloys were done at room, dry ice and liquid nitrogen temperatures by using the Mossbauer effect technique. The data were fitted by using a least squares fit from which three parameters were extracted. These parameters are the isomer shift, the quadrupole splitting and the hyperfine magnetic field. Temperature variation measurements of the hyperfine magnetic field were performed on ^{111 }Cd in Co_2MnZ (Z = Si, Ge, Sn, and Ga) alloys. The data were fitted again by using a least squares fit from which the Larmor frequency which is related to the hyperfine magnetic field was extracted. Also the Fourier Transforms were taken of the data, on the one hand to confirm the results of the least squares fit and on the other hand to look for more frequencies. Results of the Fourier Transforms show that some of the probe, ^{111}In, did go to the Co site in the Co_2MnZ (Z = Ga, Si, and Ge) alloys. The hmf on ^{111 }Cd in the Co site of these alloys is found to be 68 kOe which is consistent with the value found in the literature. Two theoretical models were examined for the trends of hyperfine magnetic field on ^{119 }Sn and ^{111}Cd in Co_2MnZ (Z = Si, Ge, Sn, and Ga) alloys. These are the Campbell and Blandin model and the Stearns' overlap model. Results show that the Campbell and Blandin model does predict the trends of the hyperfine magnetic field on ^{111}Cd but it fails in predicting any trends on ^ {119}Sn in Co_2MnZ (Z = Si, Ge, Sn, and Ga) alloys. The overlap model did not predict any trends of hmf on either probe in these alloys. A new relationship was found between the hyperfine magnetic field and the lattice constants of these alloys.

  13. Corrosion of alloy 718 in a mercury thermal convection loop

    Microsoft Academic Search

    S. J. Pawel; J. R. DiStefano; E. T. Manneschmidt

    1999-01-01

    Two thermal convection loops (TCLs) fabricated from annealed alloy 718 continuously circulated mercury (Hg) with 1000 wppm gallium (Ga), respectively, for about 5000 h, duplicating previous TCL tests for annealed 316L. In each case, the maximum loop temperature was 305C, the minimum temperature was 242C, and the Hg flow rate was approximately 1.2 m\\/min. Unlike the 316L exposed to Hg,

  14. Preliminary Experimental Measurements for a Gallium Electromagnetic (GEM) Thruster

    NASA Technical Reports Server (NTRS)

    Thomas, Robert E.; Burton, Rodney L.; Glumac, Nick G.; Polzin, Kurt A.

    2007-01-01

    A low-energy gallium plasma source is used to perform a spatially and temporally broad spectroscopic survey in the 220-520 nm range. Neutral, singly, and doubly ionized gallium are present in a 20 J, 1.8 kA (peak) arc discharge operating with a central cathode. When the polarity of the inner electrode is reversed the discharge current and arc voltage waveforms remain similar. Utilizing a central anode configuration, multiple Ga lines are absent in the 270-340 nm range. In addition, neutral and singly ionized Fe spectral lines are present, indicating erosion of the outer electrode. With graphite present on the insulator to facilitate breakdown, line emission from the gallium species is further reduced and while emissions from singly and doubly ionized carbon atoms and molecular carbon (C2) radicals are observed. These data indicate that a significant fraction of energy is shifted from the gallium and deposited into the various carbon species.

  15. Raman spectra of solid, molten, and gaseous gallium trichloride

    Microsoft Academic Search

    A. B. Salyulev; I. D. Zakiryanova

    2010-01-01

    The structure of crystalline, molten (from the melting to the critical temperature), and gaseous (at high vapor pressures)\\u000a gallium trichloride is studied by Raman spectroscopy for the first time.

  16. Gallium-67 uptake in the lung associated with metastatic calcification

    SciTech Connect

    Auerbach, J.M.; Ho, J.

    1981-03-01

    The case of a patient in whom pulmonary calcification appeared rapidly, accompanied by diffuse gallium-67 uptake in the lungs is reported. This finding, associated with metastatic calcification in the absence of inflammation or neoplasm, has not been previously reported.

  17. Lithium isotope effect accompanying electrochemical insertion of lithium into gallium

    Microsoft Academic Search

    Keita Zenzai; Satoshi Yanase; Yong-Hong Zhang; Takao Oi

    2008-01-01

    Lithium has been electrochemically inserted from a 1:2 (v\\/v) mixed solution of ethylene carbonate (EC) and methylethyl carbonate (MEC) containing 1M LiClO4 or from dimethyl sulfoxide (DMSO) containing 1M LiCl into gallium, and the lithium isotope fractionation accompanying the insertion has been observed. The lighter isotope was preferentially fractionated into gallium, which was in accordance with the theory of the

  18. Interactions of Zircaloy cladding with gallium: 1998 midyear status

    Microsoft Academic Search

    D. F. Wilson; J. R. DiStefano; J. P. Strizak; J. F. King; E. T. Manneschmidt

    1998-01-01

    A program has been implemented to evaluate the effect of gallium in mixed-oxide (MOX) fuel derived from weapons-grade (WG) plutonium on Zircaloy cladding performance. The objective is to demonstrate that low levels of gallium will not compromise the performance of the MOX fuel system in a light-water reactor. The graded, four-phase experimental program was designed to evaluate the performance of

  19. Cathodoluminescence spectra of gallium nitride nanorods

    PubMed Central

    2011-01-01

    Gallium nitride [GaN] nanorods grown on a Si(111) substrate at 720°C via plasma-assisted molecular beam epitaxy were studied by field-emission electron microscopy and cathodoluminescence [CL]. The surface topography and optical properties of the GaN nanorod cluster and single GaN nanorod were measured and discussed. The defect-related CL spectra of GaN nanorods and their dependence on temperature were investigated. The CL spectra along the length of the individual GaN nanorod were also studied. The results reveal that the 3.2-eV peak comes from the structural defect at the interface between the GaN nanorod and Si substrate. The surface state emission of the single GaN nanorod is stronger as the diameter of the GaN nanorod becomes smaller due to an increased surface-to-volume ratio. PMID:22168896

  20. Direct Band Gap Wurtzite Gallium Phosphide Nanowires

    PubMed Central

    2013-01-01

    The main challenge for light-emitting diodes is to increase the efficiency in the green part of the spectrum. Gallium phosphide (GaP) with the normal cubic crystal structure has an indirect band gap, which severely limits the green emission efficiency. Band structure calculations have predicted a direct band gap for wurtzite GaP. Here, we report the fabrication of GaP nanowires with pure hexagonal crystal structure and demonstrate the direct nature of the band gap. We observe strong photoluminescence at a wavelength of 594 nm with short lifetime, typical for a direct band gap. Furthermore, by incorporation of aluminum or arsenic in the GaP nanowires, the emitted wavelength is tuned across an important range of the visible light spectrum (555–690 nm). This approach of crystal structure engineering enables new pathways to tailor materials properties enhancing the functionality. PMID:23464761

  1. Gallium arsenide solar array subsystem study

    NASA Technical Reports Server (NTRS)

    Miller, F. Q.

    1982-01-01

    The effects on life cycle costs of a number of technology areas are examined for a gallium arsenide space solar array. Four specific configurations were addressed: (1) a 250 KWe LEO mission - planer array; (2) a 250 KWe LEO mission - with concentration; (3) a 50 KWe GEO mission planer array; (4) a 50 KWe GEO mission - with concentration. For each configuration, a baseline system conceptual design was developed and the life cycle costs estimated in detail. The baseline system requirements and design technologies were then varied and their relationships to life cycle costs quantified. For example, the thermal characteristics of the baseline design are determined by the array materials and masses. The thermal characteristics in turn determine configuration, performance, and hence life cycle costs.

  2. Direct band gap wurtzite gallium phosphide nanowires.

    PubMed

    Assali, S; Zardo, I; Plissard, S; Kriegner, D; Verheijen, M A; Bauer, G; Meijerink, A; Belabbes, A; Bechstedt, F; Haverkort, J E M; Bakkers, E P A M

    2013-04-10

    The main challenge for light-emitting diodes is to increase the efficiency in the green part of the spectrum. Gallium phosphide (GaP) with the normal cubic crystal structure has an indirect band gap, which severely limits the green emission efficiency. Band structure calculations have predicted a direct band gap for wurtzite GaP. Here, we report the fabrication of GaP nanowires with pure hexagonal crystal structure and demonstrate the direct nature of the band gap. We observe strong photoluminescence at a wavelength of 594 nm with short lifetime, typical for a direct band gap. Furthermore, by incorporation of aluminum or arsenic in the GaP nanowires, the emitted wavelength is tuned across an important range of the visible light spectrum (555-690 nm). This approach of crystal structure engineering enables new pathways to tailor materials properties enhancing the functionality. PMID:23464761

  3. Radiation damage of gallium arsenide production cells

    NASA Technical Reports Server (NTRS)

    Mardesich, N.; Garlick, G. F. J.

    1987-01-01

    High-efficiency gallium arsenide cells, made by the liquid epitaxy method (LPE), have been irradiated with 1-MeV electrons up to fluences of 10 to the 16th e/sq cm. Measurements have been made of cell spectral response and dark and light-excited current-voltage characteristics and analyzed using computer-based models to determine underlying parameters such as damage coefficients. It is possible to use spectral response to sort out damage effects in the different cell component layers. Damage coefficients are similar to other reported in the literature for the emitter and buffer (base). However, there is also a damage effect in the window layer and possibly at the window emitter interface similar to that found for proton-irradiated liquid-phase epitaxy-grown cells. Depletion layer recombination is found to be less than theoretically expected at high fluence.

  4. Gallium Arsenide solar cell radiation damage experiment

    NASA Technical Reports Server (NTRS)

    Maurer, R. H.; Kinnison, J. D.; Herbert, G. A.; Meulenberg, A.

    1991-01-01

    Gallium arsenide (GaAs) solar cells for space applications from three different manufactures were irradiated with 10 MeV protons or 1 MeV electrons. The electrical performance of the cells was measured at several fluence levels and compared. Silicon cells were included for reference and comparison. All the GaAs cell types performed similarly throughout the testing and showed a 36 to 56 percent power areal density advantage over the silicon cells. Thinner (8-mil versus 12-mil) GaAs cells provide a significant weight reduction. The use of germanium (Ge) substrates to improve mechanical integrity can be implemented with little impact on end of life performance in a radiation environment.

  5. Distinctive Signature of Indium Gallium Nitride Quantum Dot Lasing in Microdisk Cavities

    E-print Network

    Woolf, Alexander; Puchtler, Tim; Aharonovich, Igor; Zhu, Tong Tong; Niu, Nan; Wang, Danqing; Oliver, Rachel A.; Hu, Evelyn L.

    2014-01-01

    Low threshold lasers realized within compact, high quality optical cavities enable a variety of nanophotonics applications. Gallium nitride (GaN) materials containing indium gallium nitride (InGaN) quantum dots and quantum wells offer an outstanding...

  6. Application of ultrasound in solvent extraction of nickel and gallium

    SciTech Connect

    Pesic, B.

    1996-07-01

    The effects of ultrasound on the rate of solvent extraction of nickel with Lix 65N and Lix 70, and gallium with Kelex 100 were investigated. These solvent extraction systems are noted by their sluggish nature. Low frequency (20 kHz) ultrasound increased the rates of extraction of nickel by factors of four to seven. The ultrasound had no effect on the final chemical equilibrium. Gallium extraction rates were enhanced with the use of ultrasound by as much as a factor of 15. Again, the ultrasound had no effect on extraction equilibrium. For both nickel and gallium, the enhanced rates were attributed to increased interfacial surface area associated with ultrasonically induced cavitation and microdroplet formation. The stability of the microdroplets permitted intermittent application of ultrasound with corresponding decreases in ultrasonic energy requirements. The lowest energy consumption was observed with short (0.25 to 5 s) bursts of high power (41 to 61 W) ultrasonic inputs. The study also provided insight into the factors that affect the complex extraction of gallium from sodium aluminate solutions. The rate controlling step was found to be the dehydration of the gallate ion, Ga(OH)4, and the first complex formation between gallium and Kelex 100. Sodium was found to enhance the extraction rate up to a point, beyond which increased concentration was detrimental. Increasing aluminum concentration was found to slow extraction rates. Modifiers and diluents were shown to markedly affect extraction rates even without ultrasound. Ketone modifiers, particularly 2-undecanone, when used with Kermac 470B or Escaid 200 diluents enhanced extraction rates of gallium to the point that the use of ultrasound provided no additional benefits. The positive effects of ketone modifiers for the solvent extraction of gallium had not been previously reported.

  7. Preliminary Spectroscopic Measurements for a Gallium Electromagnetic (GEM) Thruster

    NASA Technical Reports Server (NTRS)

    Thomas, Robert E.; Burton, Rodney L.; Glumac, Nick G.; Polzin, Kurt A.

    2007-01-01

    As a propellant option for electromagnetic thrusters, liquid ,gallium appears to have several advantages relative to other propellants. The merits of using gallium in an electromagnetic thruster (EMT) are discussed and estimates of discharge current levels and mass flow rates yielding efficient operation are given. The gallium atomic weight of 70 predicts high efficiency in the 1500-2000 s specific impulse range, making it ideal for higher-thrust, near-Earth missions. A spatially and temporally broad spectroscopic survey in the 220-520 nm range is used to determine which species are present in the plasma and estimate electron temperature. The spectra show that neutral, singly, and doubly ionized gallium species are present in a 20 J, 1.8 kA (peak) are discharge. With graphite present on the insulator to facilitate breakdown, singly and doubly ionized carbon atoms are also present, and emission is observed from molecular carbon (CZ) radicals. A determination of the electron temperature was attempted using relative emission line data, and while the spatially and temporally averaged, spectra don't fit well to single temperatures, the data and presence of doubly ionized gallium are consistent with distributions in the 1-3 eV range.

  8. Martensitic transformation and accompanying magnetic changes in Ni-Fe-Ga-Co alloys

    NASA Astrophysics Data System (ADS)

    Sofronie, Mihaela; Tolea, Felicia; Kuncser, Victor; Valeanu, Mihaela

    2010-06-01

    Two series of cobalt substituted Ni-Fe-Ga ferromagnetic shape memory alloys with lower gallium content (<27 at. %) were studied by differential scanning calorimetry, x-ray diffraction, and thermomagnetic measurements. Co substitution for Fe or Ni promotes an increase in the Curie temperatures and a variation in the martensitic transformation (MT) temperatures, in accord with the alloy valence electron concentration change. For alloys with MTs below room temperature, a field dependent thermomagnetic hysteresis was evidenced and discussed in connection with the effect of cobalt substitution, on the magnetic hardness of the martensite phase. A direct interpretation of the evolution of the thermomagnetic hysteresis versus the applied field was provided.

  9. Measuring Nanoscale Heat Transfer for Gold-(Gallium Oxide)-Gallium Nitride Interfaces as a Function

    NASA Astrophysics Data System (ADS)

    Szwejkowski, Chester; Sun, Kai; Constantin, Costel; Giri, Ashutosh; Saltonstall, Christopher; Hopkins, Patrick; NanoSynCh Team; Exsite Team

    2014-03-01

    Gallium nitride (GaN) is considered the most important semiconductor after the discovery of Silicon. Understanding the properties of GaN is imperative in determining the utility and applicability of this class of materials to devices. We present results of time domain thermoreflectance (TDTR) measurements as a function of surface root mean square (RMS) roughness. We used commercially available 5mm x 5mm, single-side polished GaN (3-7 ?m)/Sapphire (430 ?m) substrates that have a Wurtzite crystal structure and are slightly n-type doped. The GaN substrates were annealed in the open atmosphere for 10 minutes (900-1000 °C). This high-temperature treatment produced RMS values from 1-60 nm and growth of gallium oxide (GaO) as measured with an atomic force microscopy and transmission electron microscopy respectively. A gold film (80nm) was deposited on the GaN surface using electron beam physical vapor deposition which was verified using ellipsometry and profilometry. The TDTR measurements suggest that the thermal conductivity decays exponentially with RMS roughness and that there is a minimum value for thermal boundary conductance at a roughness of 15nm.

  10. Investigation on gallium ions impacting monolayer graphene

    NASA Astrophysics Data System (ADS)

    Wu, Xin; Zhao, Haiyan; Yan, Dong; Pei, Jiayun

    2015-06-01

    In this paper, the physical phenomena of gallium (Ga+) ion impacting monolayer graphene in the nanosculpting process are investigated experimentally, and the mechanisms are explained by using Monte Carlo (MC) and molecular dynamics (MD) simulations. Firstly, the MC method is employed to clarify the phenomena happened to the monolayer graphene target under Ga+ ion irradiation. It is found that substrate has strong influence on the damage mode of graphene. The mean sputtering yield of graphene under 30 keV Ga+ ion irradiation is 1.77 and the least ion dose to completely remove carbon atoms in graphene is 21.6 ion/nm2. Afterwards, the focused ion beam over 21.6 ion/nm2 is used for the irradiation on a monolayer graphene supported by SiO2 experimentally, resulting in the nanostructures, i.e., nanodot and nanowire array on the graphene. The performances of the nanostructures are characterized by atomic force microscopy and Raman spectrum. A plasma plume shielding model is put forward to explain the nanosculpting results of graphene under different irradiation parameters. In addition, two damage mechanisms are found existing in the fabrication process of the nanostructures by using empirical MD simulations. The results can help us open the possibilities for better control of nanocarbon devices.

  11. Gallium nitride micromechanical resonators for IR detection

    NASA Astrophysics Data System (ADS)

    Rais-Zadeh, Mina

    2012-06-01

    This paper reports on a novel technology for low-noise un-cooled detection of infrared (IR) radiation using a combination of piezoelectric, pyroelectric, electrostrictive, and resonant effects. The architecture consists of a parallel array of high-Q gallium nitride (GaN) micro-mechanical resonators coated with an IR absorbing nanocomposite. The nanocomposite absorber converts the IR energy into heat with high efficiency. The generated heat causes a shift in frequency characteristics of the GaN resonators because of pyroelectric effect. IR detection is achieved by sensing the shift in the resonance frequency and amplitude of the exposed GaN resonator as compared to a reference resonator that is included in the array. This architecture offers improved signal to noise ratio compared with conventional pyroelectric detectors as the resonant effect reduces the background noise and improves sensitivity, enabling IR detection with NEDTs below 5 mK at room temperature. GaN is chosen as the resonant material as it possesses high pyroelectric, electrostrictive, and piezoelectric coefficients and can be grown on silicon substrates for low-cost batch fabrication. Measured results of a GaN IR detector prototype and a thin-film nanocomposite IR absorber are presented in this paper.

  12. Gallium nitride photocathodes for imaging photon counters

    NASA Astrophysics Data System (ADS)

    Siegmund, Oswald H. W.; Hull, Jeffrey S.; Tremsin, Anton S.; McPhate, Jason B.; Dabiran, Amir M.

    2010-07-01

    Gallium nitride opaque and semitransparent photocathodes provide high ultraviolet quantum efficiencies from 100 nm to a long wavelength cutoff at ~380 nm. P (Mg) doped GaN photocathode layers ~100 nm thick with a barrier layer of AlN (22 nm) on sapphire substrates also have low out of band response, and are highly robust. Opaque GaN photocathodes are relatively easy to optimize, and consistently provide high quantum efficiency (70% at 120 nm) provided the surface cleaning and activation (Cs) processes are well established. We have used two dimensional photon counting imaging microchannel plate detectors, with an active area of 25 mm diameter, to investigate the imaging characteristics of semitransparent GaN photocathodes. These can be produced with high (20%) efficiency, but the thickness and conductivity of the GaN must be carefully optimized. High spatial resolution of ~50 ?m with low intrinsic background (~7 events sec-1 cm-2) and good image uniformity have been achieved. Selectively patterned deposited GaN photocathodes have also been used to allow quick diagnostics of optimization parameters. GaN photocathodes of both types show great promise for future detector applications in ultraviolet Astrophysical instruments.

  13. Characterization of semi-insulating gallium arsenide

    NASA Astrophysics Data System (ADS)

    Blakemore, John S.

    1993-11-01

    The project was established 18 Nov. 1992 to continue for 12 months. Its purpose has been electrical and optical characterization of samples from semi-insulating (SI) melt-grown crystals of gallium arsenide (GaAs). As a further definition of the project's purpose, the primary goal has been to assist NRL in assessing the properties of SI GaAs crystals grown at NRL by the vertical zone melt (VZM) method. A second aspect of this characterization work has involved samples from SI GaAs crystals grown by various commercial vendors including samples of pre-synthesized GaAs evaluated for its suitability as starting 'feedstock' for VZM growth. Measurements made at Western Washington University (WWU) under the terms of this project accord with a Statement of Work provided at the outset. These have included the following: (1) low-field dc electrical transport data for SI GaAs samples, as functions of temperature; (2) near-infrared (NIR) transmittance/absorption spectra of polished slabs, with data concerning the well-known EL2 defect determined from NIR absorption strength and spectral form; and (3) mid-IR data on absorption caused by carbon acceptors in SI GaAs.

  14. Extremely-efficient, miniaturized, long-lived alpha-voltaic power source using liquid gallium

    NASA Technical Reports Server (NTRS)

    Snyder, G. Jeffrey (Inventor); Patel, Jagdishbhai (Inventor); Fleurial, Jean-Pierre (Inventor)

    2004-01-01

    A power source converts .alpha.-particle energy to electricity for use in electrical systems. Liquid gallium or other liquid medium is subjected to .alpha.-particle emissions. Electrons are freed by collision from neutral gallium atoms to provide gallium ions. The electrons migrate to a cathode while the gallium ions migrate to an anode. A current and/or voltage difference then arises between the cathode and anode because of the work function difference of the cathode and anode. Gallium atoms are regenerated by the receiving of electrons from the anode enabling the generation of additional electrons from additional .alpha.-particle collisions.

  15. First results from the Soviet-American Gallium Experiment

    SciTech Connect

    Abazov, A.I.; Abdurashitov, D.N.; Anosov, O.L.; Eroshkina, L.A.; Faizov, E.L.; Gavrin, V.N.; Kalikhov, A.V.; Knodel, T.V.; Knyshenko, I.I.; Kornoukhov, V.N.; Mezentseva, S.A.; Mirmov, I.N.; Ostrinsky, A.I.; Petukhov, V.V.; Pshukov, A.M.; Revzin, N.Y.; Shikhin, A.A.; Timofeyev, P.V.; Veretenkin, E.P.; Vermul, V.M.; Zakharov, Y.; Zatsepin, G.T.; Zhandarov, V.I. (AN SSSR, Moscow (USSR). Inst. Yadernykh Issledovanij); Bowl

    1990-01-01

    The Soviet-American Gallium Experiment is the first experiment able to measure the dominant flux of low energy p-p solar neutrinos. Four extractions made during January to May 1990 from 30 tons of gallium have been counted and indicate that the flux is consistent with 0 SNU and is less than 72 SNU (68% CL) and less than 138 SNU (95% CL). This is to be compared with the flux of 132 SNU predicted by the Standard Solar Model. 10 refs., 4 figs., 1 tab.

  16. CCMR: Gallium Nitride Nanowire Growth and FET Devices Fabrication

    NSDL National Science Digital Library

    Liu, Alison

    2005-08-17

    Being able to develop a high yield procedure where the nanowire growth can be controlled and repeated is very important for building future nanosystems. One goal of the project was to control the nanowire growth by varying different conditions such as temperature and catalyst size. Growth of gallium nitride nanowires of controlled diameters and predetermined sites has successfully been done using gold as the catalysti, but nickel nanoparticles are more difficult to use. Because of its direct band gap semiconductor properties, gallium nitride nanowires are very useful for making electronic and optical nanodevices including field-effect transistor (FET) devices. The second goal of the project was to fabricate such devices.

  17. Multiplane gallium tomography in assessment of occupational chest diseases

    SciTech Connect

    Cordasco, E.M.; O'Donnell, J.; MacIntyre, W.; Demeter, S.; Gonzalez, L.; Eren, M.; McMahon, W.; Burns, D.; Feiglin, D.H. (Cleveland Clinic Foundation, OH (USA))

    1990-01-01

    Gallium-67 scintigraphy is helpful in the evaluation of inflammatory, respiratory diseases. Single-photon emission computed tomography (SPECT) provides three-dimensional tomographic reconstruction of radioisotope distribution in the body. The addition of SPECT to gallium-67 scanning in 27 patients demonstrated an improvement in the sensitivity for detecting the presence and extent of interstitial occupational lung disease. This technique may provide earlier detection of parenchymal lung changes than can the chest x-ray and planar scanning in some patients with asbestosis. Findings in six patients with asbestosis are reported.

  18. Pseudomembranous colitis: a possible role for Gallium scanning

    SciTech Connect

    Kramer, E.L.; Charap, M.; Sanger, J.J.; Tiu, S.S.

    1983-10-01

    A case of antibiotic-associated pseudomembranous colitis is presented in which the Gallium scan was the first diagnostic modality to alert the clinicians to the existence of an inflammatory bowel process. The mechanism of localization of the radiopharmaceutical in inflammatory bowel disease is discussed. Although colonoscopy is far more specific and should be the first-line diagnostic tool used in assessing the presence of pseudomembranous colitis, Gallium scanning may have a role in the follow-up of treatment and in cases of relapse.

  19. Deep levels in gallium arsenide devices

    NASA Astrophysics Data System (ADS)

    Chen, Den Fu

    Deep-level traps can cause problems in gallium arsenide (GaAs) devices. Investigating deep level impurities in GaAs devices is the purpose of this research. Variable temperature current-voltage and capacitance-voltage measurements are used to characterize the devices. The devices are also investigated with deep level transient spectroscopy (DLTS) using lock-in amplifier DLTS and Fourier transform DLTS to identify the deep-level traps. The most important native defect in GaAs, EL2, is the main deep level impurity investigated and compared with the results of other researchers. Instead of a unique value of energy level and capture cross section, the deep level signature spreads over a wide range of values. Moreover, a strong correlation exists between the energy levels and the capture cross sections of the deep levels. To understand this correlation of energy level with capture cross section, a number of effects on the trap signature have been studied, including series resistance, leakage current, applied voltage (electric field), and various DLTS parameters. Numerical multiple-exponential fitting of the capacitance transients was used to extract the time constants of the transients. The measurement shows that the series resistance is not sufficiently significant to affect the DLTS result. The effects of reverse bias and filling pulse voltage appear significant in some cases. Data also show that there is an interaction between the pulse width and the window time on the correlation. The delay time during the early part of the capacitance transient in DLTS measurements can cause significant deviations of the extracted time constants. Fourier transform DLTS simulation shows that the signature of a deep level can vary significantly due to incorrect delay time consideration leading to a strong correlation between energy level and capture cross section.

  20. Nucleation mechanism of gallium-assisted molecular beam epitaxy growth of gallium arsenide nanowires

    SciTech Connect

    Fontcuberta i Morral, A.; Colombo, C.; Abstreiter, G.; Arbiol, J.; Morante, J. R. [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall 3, 85748 Garching (Germany); TEM-MAT, Serveis Cientificotecnics, Universitat de Barcelona, CAT, E-08080 Barcelona (Spain); EME/CeRMAE/IN2UB, Departament d'Electronica, Universitat de Barcelona, C/Marti i Franques 1, CAT, E-08080 Barcelona (Spain)

    2008-02-11

    Molecular beam epitaxy Ga-assisted synthesis of GaAs nanowires is demonstrated. The nucleation and growth are seen to be related to the presence of a SiO{sub 2} layer previously deposited on the GaAs wafer. The interaction of the reactive gallium with the SiO{sub 2} pinholes induces the formation of nanocraters, found to be the key for the nucleation of the nanowires. With SiO{sub 2} thicknesses up to 30 nm, nanocraters reach the underlying substrate, resulting into a preferential growth orientation of the nanowires. Possibly related to the formation of nanocraters, we observe an incubation period of 258 s before the nanowires growth is initiated.

  1. Synthesis of gallium nitride nanostructures by nitridation of electrochemically deposited gallium oxide on silicon substrate.

    PubMed

    Ghazali, Norizzawati Mohd; Yasui, Kanji; Hashim, Abdul Manaf

    2014-01-01

    Gallium nitride (GaN) nanostructures were successfully synthesized by the nitridation of the electrochemically deposited gallium oxide (Ga2O3) through the utilization of a so-called ammoniating process. Ga2O3 nanostructures were firstly deposited on Si substrate by a simple two-terminal electrochemical technique at a constant current density of 0.15 A/cm(2) using a mixture of Ga2O3, HCl, NH4OH and H2O for 2 h. Then, the deposited Ga2O3 sample was ammoniated in a horizontal quartz tube single zone furnace at various ammoniating times and temperatures. The complete nitridation of Ga2O3 nanostructures at temperatures of 850°C and below was not observed even the ammoniating time was kept up to 45 min. After the ammoniating process at temperature of 900°C for 15 min, several prominent diffraction peaks correspond to hexagonal GaN (h-GaN) planes were detected, while no diffraction peak of Ga2O3 structure was detected, suggesting a complete transformation of Ga2O3 to GaN. Thus, temperature seems to be a key parameter in a nitridation process where the deoxidization rate of Ga2O3 to generate gaseous Ga2O increase with temperature. The growth mechanism for the transformation of Ga2O3 to GaN was proposed and discussed. It was found that a complete transformation can not be realized without a complete deoxidization of Ga2O3. A significant change of morphological structures takes place after a complete transformation of Ga2O3 to GaN where the original nanorod structures of Ga2O3 diminish, and a new nanowire-like GaN structures appear. These results show that the presented method seems to be promising in producing high-quality h-GaN nanostructures on Si. PMID:25593562

  2. Synthesis of gallium nitride nanostructures by nitridation of electrochemically deposited gallium oxide on silicon substrate

    NASA Astrophysics Data System (ADS)

    Ghazali, Norizzawati Mohd; Yasui, Kanji; Hashim, Abdul Manaf

    2014-12-01

    Gallium nitride (GaN) nanostructures were successfully synthesized by the nitridation of the electrochemically deposited gallium oxide (Ga2O3) through the utilization of a so-called ammoniating process. Ga2O3 nanostructures were firstly deposited on Si substrate by a simple two-terminal electrochemical technique at a constant current density of 0.15 A/cm2 using a mixture of Ga2O3, HCl, NH4OH and H2O for 2 h. Then, the deposited Ga2O3 sample was ammoniated in a horizontal quartz tube single zone furnace at various ammoniating times and temperatures. The complete nitridation of Ga2O3 nanostructures at temperatures of 850°C and below was not observed even the ammoniating time was kept up to 45 min. After the ammoniating process at temperature of 900°C for 15 min, several prominent diffraction peaks correspond to hexagonal GaN (h-GaN) planes were detected, while no diffraction peak of Ga2O3 structure was detected, suggesting a complete transformation of Ga2O3 to GaN. Thus, temperature seems to be a key parameter in a nitridation process where the deoxidization rate of Ga2O3 to generate gaseous Ga2O increase with temperature. The growth mechanism for the transformation of Ga2O3 to GaN was proposed and discussed. It was found that a complete transformation can not be realized without a complete deoxidization of Ga2O3. A significant change of morphological structures takes place after a complete transformation of Ga2O3 to GaN where the original nanorod structures of Ga2O3 diminish, and a new nanowire-like GaN structures appear. These results show that the presented method seems to be promising in producing high-quality h-GaN nanostructures on Si.

  3. CCMR: Bulk GaN Growth by Gallium Vapor Transport

    NSDL National Science Digital Library

    Spinelli, Joseph

    2005-08-17

    Gallium nitride (GaN) is currently an extremely popular material used in the fabrication of many optoelectronic and electronic devices such as LEDs and LDs. Since gallium nitride is a direct band gap material there is a much more efficient output of energy. Unlike many other semiconductor materials such as silicon, which will emit a large portion of energy in the form of heat, gallium nitride emits mostly photons. The high electron mobility of the GaN results in the possibility of fabrication high frequency devices, high power devices which can be used for applications such as CD or DVD writing. The influence of high frequency or low wavelength lasers aids in the writing process by allowing more information to be stored in a smaller region of space. However the process required to fabricate high quality GaN crystals is still very costly and slow, thus holding industry back from fabricating mass quantities of GaN commercially. Bulk GaN Growth by Gallium Vapor Transport was attempted

  4. Defect levels in indium and gallium doped zinc selenide

    Microsoft Academic Search

    A. A. Qidwai; J. Woods

    1982-01-01

    Indium and gallium dopants in ZnSe display unusual properties in that although they act as shallow donors in low concentration, complex compensation effects appear to occur at high concentration, so that the resistivity increases with increasing impurity content. In order to investigate these effects, the techniques of transient photocapacitance and transient photocurrent have been used to study the incidence of

  5. Temperature Dependence of Recombination Lifetime in Gallium Arsenide Electroluminescent Diodes

    Microsoft Academic Search

    Takao Nakano; Taiji Oku

    1967-01-01

    The temperature dependence of the radiative recombination lifetime, current dependence of the externally radiated light output, and the photon energy of the radiated light in gallium arsenide electroluminescent diodes were investigated in the temperature range from 345°K to 77°K. The radiative recombination lifetime was derived by using the Shockley-Read statistics. Experimental results were analysed by this model and it was

  6. High purity liquid phase epitaxial gallium arsenide nuclear radiation detector

    Microsoft Academic Search

    Dimitri Alexiev; K. S. A. Butcher

    1992-01-01

    Surface barrier radiation detector made from high purity liquid phase epitaxial gallium arsenide wafers have been operated as X- and gamma-ray detectors at various operating temperatures. Low energy isotopes are resolved including 241Am at 40°C and the higher gamma energies of 235U at -80°C.

  7. Growth and characterization of novel gate dielectrics for gallium nitride

    Microsoft Academic Search

    Andrea H. Onstine

    2004-01-01

    Novel crystalline dielectric materials for gate application on gallium nitride were studied. These dielectric materials must operate at high temperatures and under high power loads. To meet these needs, the selected dielectric materials must be thermally stable to temperatures above 1000°C for device fabrication, must be chemically stable to prevent diffusion into the semiconductor, and must have a low defect

  8. Terbium gallium garnet Verdet constant measurements with pulsed magnetic field

    Microsoft Academic Search

    A. B. Villaverde; D. A. Donatti; D. G. Bozinis

    1978-01-01

    The dispersion of the Verdet constant of a single-crystal terbium gallium garnet (TGG) was measured using a pulsed magnetic field up to 70 KG. The data show a large Verdet constant for TGG throughout the visible region. The observed hysteresis effect is briefly discussed.

  9. THE MAGNETOCRYSTALLINE ANISOTROPY OF GALLIUM AND ALUMINIUM SUBSTITUTED MAGNETITE

    E-print Network

    Paris-Sud XI, Université de

    409 THE MAGNETOCRYSTALLINE ANISOTROPY OF GALLIUM AND ALUMINIUM SUBSTITUTED MAGNETITE By R. F of the magnetocrystalline anisotropy in magnetite (Fe3O4) as this shows a rather anomalous variation with temperature constante d'anisotropie K1 ont été mesurées de 120 °K à 400 °K par la méthode de torsion, pour sept cristaux

  10. A molecular dynamics investigation of low temperature gallium arsenide

    Microsoft Academic Search

    Joseph Irwin Landman

    1997-01-01

    An theoretical investigation of point defect and defect complexes in low temperature Gallium Arsenide (LT GaAs) has been undertaken, specifically targeting the question of the location of excess Arsenic storage in this non-stoichiometric bulk material. Molecular dynamics techniques has been used to form low energy defect configurations for study, specifically those defects which allow for an excess of Arsenic. The

  11. Discovery of Gallium, Germanium, Lutetium, and Hafnium Isotopes

    E-print Network

    Gross, J L

    2011-01-01

    Currently, twenty-eight gallium, thirty-one germanium, thirty-five lutetium, and thirty-six hafnium isotopes have been observed and the discovery of these isotopes is discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  12. Quartzhomeotypic gallium orthophosphate: A new high-tech piezoelectric crystal

    Microsoft Academic Search

    P. W. Krempl

    1997-01-01

    Piezoelectric crystals belong to the most important functional materials for the electronic and electromechanic industries. Many future technologies will demand for materials having the excellent properties owned by quartz, but higher electromechanical coupling and high thermal stability in their properties up to temperatures above 600°C. It has been demonstrated, that single crystals of quartzhomeotypic gallium orthophosphate (GaPO4) can meet all

  13. GALLIUM ARSENIDE, INDIUM PHOSPHIDE. CHEMICAL VAPOR DEPOSITION AND PHOTOLUMINESCENCE PROPERTIES

    E-print Network

    Boyer, Edmond

    783 GALLIUM ARSENIDE, INDIUM PHOSPHIDE. CHEMICAL VAPOR DEPOSITION AND PHOTOLUMINESCENCE PROPERTIES production and its good control of growth and impurity incorporation, vapor phase epitaxy seems to be more the near band gap photoluminescence (PL) of vapor grown layers needs to be improved. Since the luminescence

  14. Abnormal gallium scintigraphy in pulmonary alveolar proteinosis (PAP)

    SciTech Connect

    Yeh, S.D.; White, D.A.; Stover-Pepe, D.E.; Caravelli, J.F.; Van Uitert, C.; Benua, R.S.

    1987-04-01

    A patient with medulloblastoma of the cerebellum developed dyspnea and hypoxemia. Pulmonary function tests showed decreased lung volume and diffusing capacity, while the chest radiographs initially showed only mild interstitial infiltrates. Repeated gallium scans showed diffuse lung uptake and diagnosis of pulmonary alveolar proteinosis was made by open lung biopsy.

  15. Pair distribution function study on compression of liquid gallium

    SciTech Connect

    Luo, Shengnian [Los Alamos National Laboratory; Yu, Tony [SUNY-SB; Chen, Jiuhua [SUNY-SB; Ehm, Lars [SUNY-SB; Guo, Quanzhong [SUNY-SB; Parise, John [SUNY-SB

    2008-01-01

    Integrating a hydrothermal diamond anvil cell (HDAC) and focused high energy x-ray beam from the superconductor wiggler X17 beamline at the National Synchrotron Light Source (NSLS) at the Brookhaven National Laboratory (BNL), we have successfully collected high quality total x-ray scattering data of liquid gallium. The experiments were conducted at a pressure range from 0.1GPa up to 2GPa at ambient temperature. For the first time, pair distribution functions (PDF) for liquid gallium at high pressure were derived up to 10 {angstrom}. Liquid gallium structure has been studied by x-ray absorption (Di Cicco & Filipponi, 1993; Wei et al., 2000; Comez et al., 2001), x-ray diffraction studies (Waseda & Suzuki, 1972), and molecular dynamics simulation (Tsay, 1993; Hui et al., 2002). These previous reports have focused on the 1st nearest neighbor structure, which tells us little about the atomic arrangement outside the first shell in non- crystalline materials. This study focuses on the structure of liquid gallium and the atomic structure change due to compression. The PDF results show that the observed atomic distance of the first nearest neighbor at 2.78 {angstrom} (first G(r) peak and its shoulder at the higher Q position) is consistent with previous studies by x-ray absorption (2.76 {angstrom}, Comez et al., 2001). We have also observed that the first nearest neighbor peak position did not change with pressure increasing, while the farther peaks positions in the intermediate distance range decreased with pressure increasing. This leads to a conclusion of the possible existence of 'locally rigid units' in the liquid. With the addition of reverse Monte Carlo modeling, we have observed that the coordination number in the local rigit unit increases with pressure. The bulk modulus of liquid gallium derived from the volume compression curve at ambient temperature (300K) is 12.1(6) GPa.

  16. Self- and zinc diffusion in gallium antimonide

    SciTech Connect

    Nicols, Samuel Piers

    2002-03-26

    The technological age has in large part been driven by the applications of semiconductors, and most notably by silicon. Our lives have been thoroughly changed by devices using the broad range of semiconductor technology developed over the past forty years. Much of the technological development has its foundation in research carried out on the different semiconductors whose properties can be exploited to make transistors, lasers, and many other devices. While the technological focus has largely been on silicon, many other semiconductor systems have applications in industry and offer formidable academic challenges. Diffusion studies belong to the most basic studies in semiconductors, important from both an application as well as research standpoint. Diffusion processes govern the junctions formed for device applications. As the device dimensions are decreased and the dopant concentrations increased, keeping pace with Moore's Law, a deeper understanding of diffusion is necessary to establish and maintain the sharp dopant profiles engineered for optimal device performance. From an academic viewpoint, diffusion in semiconductors allows for the study of point defects. Very few techniques exist which allow for the extraction of as much information of their properties. This study focuses on diffusion in the semiconductor gallium antimonide (GaSb). As will become clear, this compound semiconductor proves to be a powerful one for investigating both self- and foreign atom diffusion. While the results have direct applications for work on GaSb devices, the results should also be taken in the broader context of III-V semiconductors. Results here can be compared and contrasted to results in systems such as GaAs and even GaN, indicating trends within this common group of semiconductors. The results also have direct importance for ternary and quaternary semiconductor systems used in devices such as high speed InP/GaAsSb/InP double heterojunction bipolar transistors (DHBT) [Dvorak, (2001)]. Many of the findings which will be reported here were previously published in three journal articles. Hartmut Bracht was the lead author on two articles on self-diffusion studies in GaSb [Bracht, (2001), (2000)], while this report's author was the lead author on Zn diffusion results [Nicols, (2001)]. Much of the information contained herein can be found in those articles, but a more detailed treatment is presented here.

  17. (Data in kilograms of gallium content, unless noted) Domestic Production and Use: No domestic primary gallium recovery was reported in 1995. Two companies in

    E-print Network

    .S. gallium consumption, were valued at about $3.5 million. Gallium arsenide (GaAs) components represented, submicron semiconductor device manufacturing, and medical applications. As one step to developing high semiconductor chip. This type of component can be used for processing optical signals, such as infrared light

  18. Corrosion of alloy 718 in a mercury thermal convection loop

    SciTech Connect

    Pawel, S.J.; DiStefano, J.R.; Manneschmidt, E.T.

    1999-12-01

    Two thermal convection loops (TCLs) fabricated from annealed alloy 718 continuously circulated mercury (Hg) with 1000 wppm gallium (Ga), respectively, for about 5000 h, duplicating previous TCL tests for annealed 316L. In each case, the maximum loop temperature was 305C, the minimum temperature was 242C, and the Hg flow rate was approximately 1.2 m/min. Unlike the 316L exposed to Hg, which above about 260C exhibited a thin, porous surface layer depleted in Ni and Cr, the alloy 718 coupons revealed essentially no wetting and, therefore, no interaction with that Hg at any temperature. Alloy 718 coupons suspended in the loops revealed inconsequentially small weight changes, and both the coupons and loop tubing exhibited no detectable metallographic evidence of attack.

  19. Photoelectrochemical etching of gallium nitride for high quality optical devices

    NASA Astrophysics Data System (ADS)

    Tamboli, Adele C.

    Gallium nitride has become an important semiconductor material for a variety of device applications, including light emitting diodes (LEDs), lasers, and transistors. One of the main challenges in GaN device fabrication is the chemical stability of GaN which leads to a lack of wet etching techniques. Instead, dry etching is used almost exclusively, leading to ion damage and poor selectivity between different layers. In this dissertation, we discuss photoelectrochemical (PEC) etching, a photoassisted wet etch technique that can be used to etch GaN and its alloys. We develop new aspects of this technique to extend its applicability to a larger variety of devices and use the technique to fabricate a few optical devices, including microdisk lasers. Microdisks are circular resonant cavities that support whispering gallery modes, which propagate around the periphery of the disk, confined by total internal reflection. This geometry has been used to achieve high quality modes, small mode volume, and low threshold lasing in semiconductors such as GaAs and InGaAsP, but has been difficult to fabricate in GaN because it requires a selective wet etch to form undercut, optically isolated cavities. In this dissertation, we discuss the application of PEC etching to the fabrication of GaN microdisks. In our optically pumped, c-plane microdisks, we observe record low threshold lasing under room temperature, continuous-wave operation. In our nonpolar m-plane microdisks, we discovered that the quantum well reabsorption losses that reduce the efficiency of many GaAs and InP microdisks also limit the performance of our nonpolar microdisks, while the piezoelectric fields and corresponding Stokes shift in our c-plane microdisks lead to quantum-dot like behavior and actually lead to superior performance in the polar, c-planemicrodisks. Finally, we report of electrically driven operation of c-plane microdisks for the first time. In these microdisks, first order whispering gallery modes are observed under both optical and electrical injection. We also examine new applications of PEC etching in this dissertation. We have discovered that m-plane GaN, grown homoepitaxially on bulk GaN substrates, etches much more smoothly and predictably than c-plane GaN on sapphire because of the lower defect density and reduced chemical stability of the nonpolar facets. We are able to obtain highly bandgap-selective top-down etching, deep, anisotropic etching, and etches with angled facets. These etch studies open up the possibility of a variety of new m-plane devices fabricated with PEC etching, such as chip-shaped LEDs. We also develop a method for PEC etching of p-type GaN, which has been very difficult to achieve in any semiconductor system. We apply this technique to surface roughening of the p-type, Ga-face side of c-plane LEDs, increasing the light extraction efficiency without the need for flip-chip bonding or substrate removal.

  20. Mechanical Alloying

    Microsoft Academic Search

    J. S. Benjamin

    1976-01-01

    A new technique of combining metals has been developed which overcomes many of the limitations of conventional alloying. Ball mills that generate higher energies than conventional ball mills are used to tumble a mixture of powders, such as WC and Co, in order to form a composite. Ni-base alloys can be dispersion-hardened in this way with an oxide such as

  1. Arene complexes of gallium: An effective tool for the synthesis of transition metal clusters and complexes

    Microsoft Academic Search

    Mikhail Gorlov; Lars Kloo

    2008-01-01

    In this review, the interactions between gallium(III) halides or gallium(I) subvalent halides and aromatic hydrocarbons in solution and solid state are discussed. Such unique properties of gallium halides–arene mixtures as the ability to reduce metallic centers and accept halide atoms make them very efficient tool for the preparation of low-valent clusters and complexes of transition metals. Diverse mono- and polynuclear

  2. The magnetostriction of rare-earth garnets containing gallium and europium: Old theory for new problems

    Microsoft Academic Search

    R. White

    1973-01-01

    A calculation is made of the effect of gallium substitution upon the magnetostriction of rare-earth garnets, a problem of some interest because of the use of gallium substituted garnets as bubble-domain materials. The gallium alters the contribution to magnetostriction of the iron lattices by simple dilution and of the rare-earth lattice by reducing the exchange field acting upon the rare-earth

  3. Enhanced thermal stability of alpha gallium oxide films supported by aluminum doping

    NASA Astrophysics Data System (ADS)

    Lee, Sam-Dong; Ito, Yoshito; Kaneko, Kentaro; Fujita, Shizuo

    2015-03-01

    In order to enhance the thermal stability of corundum-structured gallium oxide (?-Ga2O3), which is attractive for use in wide-band-gap heterostructure devices and amenable to band gap and function engineering but suffers from phase transformation in high-temperature growth (>500 °C) and treatments (>550 °C), we attempted aluminum (Al) doping. The thermal stability of the films was enhanced by increasing the Al doping concentration, and under the best doping conditions where the Al concentration was negligible compared with the basic chemical composition of Ga2O3, the growth and successive thermal treatment temperatures were increased to as high as 650 and 750 °C, respectively, without the marked appearance of the ?-gallia phase. Under the doping conditions above, the inclusion of Al was not negligible at the growth temperature of 800 °C and the film composition was expressed as an alloy of ?-(Al0.2Ga0.8)2O3, but this film remained as the ?-phase at annealing temperatures up to 900 °C. Enhanced thermal stability widens the device process windows, contributing to the formation of various high-performance devices.

  4. Gallium-Cooled Target for Compact Accelerator-Based Neutron Sources

    NASA Astrophysics Data System (ADS)

    Carpenter, John M.

    This paper discusses the motivation for gallium cooling of targets of compact accelerator-based neutron sources (CANS); summarizes features of the low-power alternative, i.e., water cooling, and the limitations of boiling water heat transfer; lists the properties of liquid gallium; and cites its low hazards potential. I set out working equations for heat transport and fluid flow in liquid gallium and present a concept for a gallium-cooled system, including a scoping calculation of temperatures and pressure drops, and present conclusions and a recommendation.

  5. Aging and memory effect in magnetoelectric gallium ferrite single crystals

    NASA Astrophysics Data System (ADS)

    Singh, Vijay; Mukherjee, Somdutta; Mitra, Chiranjib; Garg, Ashish; Gupta, Rajeev

    2015-02-01

    Here, we present a time and temperature dependent magnetization study to understand the spin dynamics in flux grown single crystals of gallium ferrite (GaFeO3), a known magnetoelectric, ferroelectric and ferrimagnet. Results of the magnetic measurements conducted in the field-cooled (FC) and zero-field-cooled (ZFC) protocols in the heating and cooling cycles were reminiscent of a "memory" effect. Subsequent time dependent magnetic relaxation measurements carried out in ZFC mode at 30 K with an intermittent cooling to 20 K in the presence of a small field show that the magnetization in the final wait period tends to follow its initial state which was present before the cooling break taken at 20 K. These observations provide an unambiguous evidence of single crystal gallium ferrite having a spin glass like phase.

  6. Thermodynamic properties of liquid gallium from picosecond acoustic velocity measurements

    NASA Astrophysics Data System (ADS)

    Ayrinhac, S.; Gauthier, M.; Le Marchand, G.; Morand, M.; Bergame, F.; Decremps, F.

    2015-07-01

    Due to discrepancies in the literature data the thermodynamic properties of liquid gallium are still in debate. Accurate measurements of adiabatic sound velocities as a function of pressure and temperature have been obtained by the combination of laser picosecond acoustics and surface imaging on sample loaded in diamond anvil cell. From these results the thermodynamic parameters of gallium have been extracted by a numerical procedure up to 10 GPa and 570 K. It is demonstrated that a Murnaghan equation of state accounts well for the whole data set since the isothermal bulk modulus BT has been shown to vary linearly with pressure in the whole temperature range. No evidence for a previously reported liquid–liquid transition has been found in the whole pressure and temperature range explored.

  7. Thermodynamic properties of liquid gallium from picosecond acoustic velocity measurements.

    PubMed

    Ayrinhac, S; Gauthier, M; Le Marchand, G; Morand, M; Bergame, F; Decremps, F

    2015-07-15

    Due to discrepancies in the literature data the thermodynamic properties of liquid gallium are still in debate. Accurate measurements of adiabatic sound velocities as a function of pressure and temperature have been obtained by the combination of laser picosecond acoustics and surface imaging on sample loaded in diamond anvil cell. From these results the thermodynamic parameters of gallium have been extracted by a numerical procedure up to 10 GPa and 570 K. It is demonstrated that a Murnaghan equation of state accounts well for the whole data set since the isothermal bulk modulus BT has been shown to vary linearly with pressure in the whole temperature range. No evidence for a previously reported liquid-liquid transition has been found in the whole pressure and temperature range explored. PMID:26061830

  8. Hydrothermal preparation and characterization of nanocrystalline. Silver gallium sulfides

    NASA Astrophysics Data System (ADS)

    Junqing, Hu; Bin, Deng; Kaibin, Tang; Qingyi, Lu; Rongrong, Jiang; Yitai, Qian

    2001-03-01

    The hydrothermal reaction route was developed to prepare nanocrystalline silver gallium sulfides AgGaS 2 and ?-Ag 9GaS 6, respectively. X-ray powder diffraction patterns indicated tetragonal phase AgGaS 2 with cell constants a=5.765 and c=10.281 Å, and orthorhombic phase ?-Ag 9GaS 6 with cell constants a=10.756, b=7.806, and c=7.605 Å. Transmission electron microscopy images revealed that nanocrystalline AgGaS 2 consisted of uniform spherical particles with grain sizes of 6-12 nm and nanocrystalline ?-Ag 9GaS 6 displayed whisker-like particles with an average size of 20×5 nm. The room temperature photoluminescence spectrum of nanocrystalline AgGaS 2 was found to be one broad emission feature at 446 nm. A possible formation mechanism of silver gallium sulfides was proposed.

  9. Preparation Of Copper Indium Gallium Diselenide Films For Solar Cells

    DOEpatents

    Bhattacharya, Raghu N. (Littleton, CO); Contreras, Miguel A. (Golden, CO); Keane, James (Lakewood, CO); Tennant, Andrew L. (Denver, CO), Tuttle, John R. (Denver, CO); Ramanathan, Kannan (Lakewood, CO); Noufi, Rommel (Golden, CO)

    1998-08-08

    High quality thin films of copper-indium-gallium-diselenide useful in the production of solar cells are prepared by electrodepositing at least one of the constituent metals onto a glass/Mo substrate, followed by physical vapor deposition of copper and selenium or indium and selenium to adjust the final stoichiometry of the thin film to approximately Cu(In,Ga)Se.sub.2. Using an AC voltage of 1-100 KHz in combination with a DC voltage for electrodeposition improves the morphology and growth rate of the deposited thin film. An electrodeposition solution comprising at least in part an organic solvent may be used in conjunction with an increased cathodic potential to increase the gallium content of the electrodeposited thin film.

  10. Optical and acoustic phonon modes confined in gallium phosphide nanoparticles

    Microsoft Academic Search

    Zhaochun Zhang; Neng Zhang

    2010-01-01

    The main aim of this paper is to discuss the confinement effects on the optical and acoustic phonon vibrational modes in gallium\\u000a phosphide (GaP) nanoparticles (cylindric grain). The Raman scattering from the GaP nanoparticles was investigated. It was\\u000a found that the red-shifts of the longitudinal optical (LO) mode and transverse optical (TO) mode were 15 cm?1 and 13.8 cm?1, respectively.

  11. Copper Indium Gallium Selenide photovoltaic modules manufactured by reactive transfer

    Microsoft Academic Search

    Dingyuan Lu; Baosheng Sang; Yuepeng Deng; B. J. Stanbery; L. Eldada

    2010-01-01

    In recent years, thin-film photovoltaic companies, especially First Solar with its CdTe technology, managed to realize the low manufacturing cost potential and to grab an increasingly larger market share. Copper Indium Gallium Selenide is the most promising thin-film PV material, having demonstrated the highest energy conversion efficiency in both cells and modules. However, most CIGS manufacturers still face the challenge

  12. Incorporation of copper into indium gallium selenide layers from solution

    Microsoft Academic Search

    C. J. Hibberd; M. Ganchev; M. Kaelin; K. Ernits; A. N. Tiwari

    2008-01-01

    A chemical method for the incorporation of copper into indium gallium selenide (IGS) layers has been developed. The resulting copper-containing precursor layers have been annealed in the presence of selenium vapour with the goal of forming Cu(In, Ga)Se2 (CIGS) layers. It is found that copper ions in solution are incorporated into IGS layers during immersion, resulting in the formation of

  13. Intrinsic noise characteristics of gallium nitride high electron mobility transistors

    Microsoft Academic Search

    Sungjae Lee

    2004-01-01

    Wide bandgap gallium nitride high electron mobility transistors (GaN HEMTs) have recently been developed for microwave sources and amplifiers. An experimental and numerical modeling effort is presented to study noise mechanisms within GaN HEMTs. This allows an equivalent-circuit model to be established, facilitating the extraction of intrinsic noise and also microwave circuit design. ^ Intrinsic noise sources in GaN HEMTs

  14. Spectral properties of proton irradiated gallium nitride blue diodes

    Microsoft Academic Search

    François Gaudreau; Cosmo Carlone; Alain Houdayer; Shyam M. Khanna

    2001-01-01

    The permanent damage induced by 2 MeV proton irradiation at room temperature is reported for gallium nitride based blue emitting diodes (CREE model C430-DH85). Both optical and electrical device characteristics were measured. The I-V dependence was obtained as a function of temperature. At low voltages, the current is proportional to the exponential of the voltage at a constant temperature and

  15. Behavior of Zircaloy Cladding in the Presence of Gallium

    Microsoft Academic Search

    J. R. DiStefano; J. F. King; E. T. Manneschmidt; J. P. Strizak; D. F. Wilson

    1998-01-01

    The U.S. Department of Energy has established a dual-track approach to the disposition of plutonium arising from the dismantling of nuclear weapons. Both immobilization and reactor-based mixed-oxide (MOX) fuel technologies are being evaluated. The reactor-based MOX fuel option requires assessment of the potential impact of concentrations of gallium (on the order of 1 to 10 ppm), not present in conventional

  16. Interactions of Zircaloy Cladding with Gallium: Final Report

    Microsoft Academic Search

    D. F. Wilson; E. T. Manneschmidt; J. F. King; J. P. Strizak; J. R. DiStefano

    1998-01-01

    The U.S. Department of Energy has established a dual-track approach to the disposition of plutonium arising from the dismantling of nuclear weapons. Both immobilization and reactor-based mixed-oxide (MOX) fuel technologies are being evaluated. The reactor-based MOX fuel option requires assessment of the potential impact of concentrations of gallium (on the order of 1 to 10 ppm), not present in conventional

  17. A gallium phosphide high-temperature bipolar junction transistor

    Microsoft Academic Search

    T. E. Zipperian; L. R. Dawson; R. J. Caffin

    1981-01-01

    Preliminary results are reported on the development of a high-temperature (> 350°C) gallium phosphide bipolar junction transistor (BJT) for goethermal and other energy applications. This four-layer p\\/sup +\\/n⁻pp\\/sup +\\/ structure was fromed by liquid phase epitaxy using a supercooling technique to insure uniform nucleation of the thin layers. Magnesium was used as the p-type dopant to avoid excessive out-diffusion into

  18. Synthesis and photonic applications of gallium nitride nanowires

    Microsoft Academic Search

    S. Han; Wu Jin; Tao Tang; C. Zhou

    2003-01-01

    High quality single crystal gallium nitride nanowires (GaN NWs) are synthesized with a novel chemical vapor deposition (CVD) method. Transport studies of single crystal GaN nanowire devices exhibit n-type transistor behavior with high electron mobility. Ultraviolet (UV) light sensors are fabricated with GaN NW devices. The nanowire sensors exhibited a substantial increase in conductance upon UV light exposure. In addition

  19. Terahertz Cherenkov radiation from ultrafast magnetization in terbium gallium garnet

    NASA Astrophysics Data System (ADS)

    Gorelov, S. D.; Mashkovich, E. A.; Tsarev, M. V.; Bakunov, M. I.

    2013-12-01

    We report an experimental observation of terahertz Cherenkov radiation from a moving magnetic moment produced in terbium gallium garnet by a circularly polarized femtosecond laser pulse via the inverse Faraday effect. Contrary to some existing theoretical predictions, the polarity of the observed radiation unambiguously demonstrates the paramagnetic, rather than diamagnetic, nature of the ultrafast inverse Faraday effect. From measurements of the radiation field, the Verdet constant in the subpicosecond regime is ˜3-10 times smaller than its table quasistatic value.

  20. Accurate Acoustic Thermometry I: The Triple Point of Gallium

    Microsoft Academic Search

    M R Moldover; J P M Trusler

    1988-01-01

    The speed of sound in argon has been accurately measured in the pressure range 25-380 kPa at the temperature of the triple point of gallium (Tg) and at 340 kPa at the temperature of the triple point of water (Tt). The results are combined with previously published thermodynamic and transport property data to obtain Tg = (302.9169 ± 0.0005) K

  1. Accurate Acoustic Thermometry I: The Triple Point of Gallium

    Microsoft Academic Search

    M. R. Moldover; J. P. M. Trusler

    1988-01-01

    The speed of sound in argon has been accurately measured in the pressure range 25-380 kPa at the temperature of the triple point of gallium (Tg) and at 340 kPa at the temperature of the triple point of water (Tt). The results are combined with previously published thermodynamic and transport property data to obtain Tg = (302.9169 +\\/- 0.0005) K

  2. INDIUM PHOSPHIDE WINDOW LAYERS FOR INDIUM GALLIUM ARSENIDE SOLAR CELLS

    Microsoft Academic Search

    Raj K. Jain

    Window layers help in reducing the surface recombination at the emitter surface of the solar cells re- sulting in significant improvement in energy conversion efficiency. Indium gallium arsenide (InxGa1-xAs) and related materials based solar cells are quite promising for photovoltaic and thermophotovoltaic applications. The flexibility of the change in the bandgap energy and the growth of InGaAs on different substrates

  3. A high open-circuit voltage gallium nitride betavoltaic microbattery

    Microsoft Academic Search

    Zaijun Cheng; Xuyuan Chen; Haisheng San; Zhihong Feng; Bo Liu

    2012-01-01

    A high open-circuit voltage betavoltaic microbattery based on a gallium nitride (GaN) p–i–n homojunction is demonstrated. As a beta-absorbing layer, the low electron concentration of the n-type GaN layer is achieved by the process of Fe compensation doping. Under the irradiation of a planar solid 63Ni source with activity of 0.5 mCi, the open-circuit voltage of the fabricated microbattery with

  4. Improved performance design of gallium arsenide solar cells for space

    Microsoft Academic Search

    R. H. Parekh; A. M. Barnett

    1984-01-01

    Two gallium arsenide solar cell configurations have evolved over the last decade--the heteroface solar cell which uses a (GaAl) as surface passivating layer over a p-n solar cell; and a n\\/sup +\\/-p-p\\/sup +\\/ shallow homojunction solar cell. Energy conversion efficiencies of 18.8 percent have been reported with the heteroface structure. In this paper, we report an improved design, shallow junction

  5. Fabrication of a gated gallium arsenide heterostructure resonant tunneling diode

    E-print Network

    Kinard, William Brian

    1989-01-01

    -dimensional confinement of i arriers in the potential ivell. Additionally, very interesting and unique transport phenomena are expected to emerge from further experimentation with the fabricated devices and other devices improved fr irii this technology. This thesis... removed organic material left by the previous solvent. The ivafers were then agitated in diluted hy- drochloric acid to remove any remaining metal contamination v, hile dissolving anv native gallium oxide on the surface. The &vafcrs were then rinsed...

  6. Deprotecting Thioacetyl-Terminated Terphenyldithiol for Assembly on Gallium Arsenide

    Microsoft Academic Search

    Dmitry A. Krapchetov; Hong Ma; Alex K. Y. Jen; Daniel A. Fischer; Yueh-Lin Loo

    2008-01-01

    We characterize the assembly of terphenyldithiol (TPDT) on gallium arsenide (GaAs) from ethanol (EtOH) and tetrahydrofuran (THF) as a function of ammonium hydroxide (NH4OH) concentration. NH4OH facilitates the conversion of thioacetyl end groups of the TPDT precursor to thiolates in the assembly solution. The final structure of TPDT assembled on GaAs is sensitive not only to the assembly solvent but

  7. Use of Gallium-67 in the diagnosis of occult infections

    SciTech Connect

    Hoffer, P.B.

    1981-05-01

    The mechanism of Ga-67 citrates in the diagnosis of infection involves the rapid binding of gallium by transferrin. The Ga-67-transferrin complex gains access into inflammatory tissue to some extent through the leaky endothelium of vessels at sites of inflammation. In addition, Ga-67 binds to a limited extent to circulating neutrophils. Advances in imaging techniques using Ga-67 citrates are discussed. The clinical applications include the diagnosis of bone and joint infections, pulmonary lesions, and infections of the urinary tract.

  8. TUNABLE TERAHERTZ GENERATION IN QUASI-PHASEMATCHED GALLIUM ARSENIDE

    Microsoft Academic Search

    Joseph E. Schaar; Konstantin L. Vodopyanov; Martin M. Fejer

    Sources of electromagnetic radiation with terahertz (THz) frequencies have been actively investigated during the last decade for applications in imaging and spectroscopic sensors. Femtosecond optical pulses have been shown to efficiently generate THz waves in quasi-phasematched (QPM) gallium arsenide (GaAs) (1). In this work we demonstrate a picosecond system creating a near diffraction-limited THz source with 1 mW of average

  9. POLLUTION PREVENTION IN THE SEMICONDUCTOR INDUSTRY THROUGH RECOVERY AND RECYCLING OF GALLIUM AND ARSENIC FROM GAAS POLISHING WASTES

    EPA Science Inventory

    A process was developed for the recovery of both arsenic and gallium from gallium arsenide polishing wastes. The economics associated with the current disposal techniques utilizing ferric hydroxide precipitation dictate that sequential recovery of toxic arsenic and valuble galliu...

  10. Characterization of alkaline manganese dioxide products containing no lead added zinc alloys

    SciTech Connect

    West, J.T.; Bonacker, F.F. [Rayovac Corp., Madison, WI (United States)

    1995-12-31

    Environmental pressures have resulted in major efforts by consumer battery manufacturers to significantly reduce the toxic heavy-metal content of alkaline manganese dioxide cells. The performance characteristics of mercury- and cadmium-free products containing no lead-added zinc alloys have been evaluated and compared to mercury and cadmium-free products containing lead-bearing alloys. The effects of the absence of mercury, cadmium and lead are reported. The efforts of the battery industry to deal with the observed problems is reflected in awarded patents and an abundance of patent applications involving the group of metals: bismuth, indium, gallium, thallium, calcium, aluminum, and strontium.

  11. Appraisal of lupus nephritis by renal imaging with gallium-67

    SciTech Connect

    Bakir, A.A.; Lopez-Majano, V.; Hryhorczuk, D.O.; Rhee, H.L.; Dunea, G.

    1985-08-01

    To assess the activity of lupus nephritis, 43 patients with systemic lupus erythematosus (SLE) were studied by gallium imaging. Delayed renal visualization 48 hours after the gallium injection, a positive result, was noted in 25 of 48 scans. Active renal disease was defined by the presence of hematuria, pyuria (10 or more red blood cells or white blood cells per high-power field), proteinuria (1 g or more per 24 hours), a rising serum creatinine level, or a recent biopsy specimen showing proliferative and/or necrotizing lesions involving more than 20 percent of glomeruli. Renal disease was active in 18 instances, inactive in 23, and undetermined in seven (a total of 48 scans). Sixteen of the 18 scans (89 percent) in patients with active renal disease showed positive findings, as compared with only four of 23 scans (17 percent) in patients with inactive renal disease (p less than 0.001). Patients with positive scanning results had a higher rate of hypertension (p = 0.02), nephrotic proteinuria (p = 0.01), and progressive renal failure (p = 0.02). Mild mesangial nephritis (World Health Organization classes I and II) was noted only in the patients with negative scanning results (p = 0.02) who, however, showed a higher incidence of severe extrarenal SLE (p = 0.04). It is concluded that gallium imaging is a useful tool in evaluating the activity of lupus nephritis.

  12. Defects in gallium nitride nanowires: first principles calculations

    SciTech Connect

    Wang, Zhiguo; Li, Jingbo; Gao, Fei; Weber, William J.

    2010-08-15

    Atomic configurations and formation energies of native defects in an unsaturated GaN nanowire grown along the [001] direction and with (100) lateral facets are studied using large-scale ab initio calculation. Cation and anion vacancies, antisites and interstitials in the neutral charge state are all considered. The nitrogen related defects are more stable than the gallium related defects under nitrogen-rich conditions. The configurations of these defects in the core region of the nanowire are same as those in the bulk GaN. The relaxation of vacancies is generally small, but the relaxation around antisite defects is large. The nitrogen interstitial relaxes into a split interstitial configuration. The configurations of the defects in the outermost free surface region are different than those in the core. A Ga atom on the outmost surface is replaced by a Ga interstital, and is ejected on to the surface to become an adsorbed atom. A gallium atom at the outermost surface can also be ejected out to become an adsorbed atom. Nitrogen interstitials form a split-interstitial configuration with one of the nearest-neighbor nitrogens. For a Ga vacancy at the edge of the side plane of the nanowire, nitrogen atom at a gallium site and nitrogen interstitial often induced the formation of N2 molecules with low formation energy, which agrees well with experiment findings [Nano Letters 9, 1844 (2009)].

  13. Pollution prevention in the semiconductor industry through recovery and recycling of gallium and arsenic from GaAs polishing wastes

    Microsoft Academic Search

    J. A. Sturgill; J. T. Swartzbaugh; P. M. Randall

    2000-01-01

    A process was developed for the recovery of both arsenic and gallium from gallium arsenide polishing wastes. The economics\\u000a associated with the current disposal techniques utilizing ferric hydroxide precipitation dictate that sequential recovery\\u000a of toxic arsenic and valuable gallium, with subsequent purification and in-house reuse of both, is to the benefit of the gallium\\u000a arsenide crystal grower. The developed process

  14. Smooth cubic commensurate oxides on gallium nitride

    SciTech Connect

    Paisley, Elizabeth A.; Gaddy, Benjamin E.; LeBeau, James M.; Shelton, Christopher T.; Losego, Mark D.; Mita, Seiji; Collazo, Ramón; Sitar, Zlatko; Irving, Douglas L.; Maria, Jon-Paul, E-mail: jpmaria@ncsu.edu [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Biegalski, Michael D.; Christen, Hans M. [Center for Nanophase Materials Science, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

    2014-02-14

    Smooth, commensurate alloys of ?111?-oriented Mg{sub 0.52}Ca{sub 0.48}O (MCO) thin films are demonstrated on Ga-polar, c+ [0001]-oriented GaN by surfactant-assisted molecular beam epitaxy and pulsed laser deposition. These are unique examples of coherent cubic oxide|nitride interfaces with structural and morphological perfection. Metal-insulator-semiconductor capacitor structures were fabricated on n-type GaN. A comparison of leakage current density for conventional and surfactant-assisted growth reveals a nearly 100× reduction in leakage current density for the surfactant-assisted samples. HAADF-STEM images of the MCO|GaN interface show commensurate alignment of atomic planes with minimal defects due to lattice mismatch. STEM and DFT calculations show that GaN c/2 steps create incoherent boundaries in MCO over layers which manifest as two in-plane rotations and determine consequently the density of structural defects in otherwise coherent MCO. This new understanding of interfacial steps between HCP and FCC crystals identifies the steps needed to create globally defect-free heterostructures.

  15. Smooth cubic commensurate oxides on gallium nitride

    NASA Astrophysics Data System (ADS)

    Paisley, Elizabeth A.; Gaddy, Benjamin E.; LeBeau, James M.; Shelton, Christopher T.; Biegalski, Michael D.; Christen, Hans M.; Losego, Mark D.; Mita, Seiji; Collazo, Ramón; Sitar, Zlatko; Irving, Douglas L.; Maria, Jon-Paul

    2014-02-01

    Smooth, commensurate alloys of ?111?-oriented Mg0.52Ca0.48O (MCO) thin films are demonstrated on Ga-polar, c+ [0001]-oriented GaN by surfactant-assisted molecular beam epitaxy and pulsed laser deposition. These are unique examples of coherent cubic oxide|nitride interfaces with structural and morphological perfection. Metal-insulator-semiconductor capacitor structures were fabricated on n-type GaN. A comparison of leakage current density for conventional and surfactant-assisted growth reveals a nearly 100× reduction in leakage current density for the surfactant-assisted samples. HAADF-STEM images of the MCO|GaN interface show commensurate alignment of atomic planes with minimal defects due to lattice mismatch. STEM and DFT calculations show that GaN c/2 steps create incoherent boundaries in MCO over layers which manifest as two in-plane rotations and determine consequently the density of structural defects in otherwise coherent MCO. This new understanding of interfacial steps between HCP and FCC crystals identifies the steps needed to create globally defect-free heterostructures.

  16. Gain-guided aluminum gallium arsenide-gallium arsenide quantum-well heterostructure lasers fabricated by hydrogenation

    Microsoft Academic Search

    1988-01-01

    New fabrication techniques that are simple and easily implemented with present technology may have an impact on laser manufacturing. Hydrogenation is such a process. Hydrogen compensation of shallow impurities is studied in aluminum gallium arsenide. Data are presented showing the effects of exposure to a hydrogen plasma on n-type GaAs and both n- and p-type Al{sub 0.75}Ga{sub 0.25}As. Samples are

  17. Zintl cluster chemistry in the alkali-metal-gallium systems

    SciTech Connect

    Henning, R.

    1998-03-27

    Previous research into the alkali-metal-gallium systems has revealed a large variety of networked gallium deltahedra. The clusters are analogues to borane clusters and follow the same electronic requirements of 2n+2 skeletal electrons for closo-deltahedra. This work has focused on compounds that do not follow the typical electron counting rules. The first isolated gallium cluster was found in Cs{sub 8}Ga{sub 11}. The geometry of the Ga{sub 11}{sup 7{minus}} unit is not deltahedral but can be described as a penta-capped trigonal prism. The reduction of the charge from a closo-Ga{sub 11}{sup 13{minus}} to Ga{sub 11}{sup 7{minus}} is believed to be the driving force of the distortion. The compound is paramagnetic because of an extra electron but incorporation of a halide atom into the structure captures the unpaired electron and forms a diamagnetic compound. A second isolated cluster has been found in Na{sub 10}Ga{sub 10}Ni where the tetra-capped trigonal prismatic gallium is centered by nickel. Stabilization of the cluster occurs through Ni-Ga bonding. A simple two-dimensional network occurs in the binary K{sub 2}Ga{sub 3} Octahedra are connected through four waist atoms to form a layered structure with the potassium atoms sitting between the layers. Na{sub 30.5}Ga{sub 60{minus}x}Ag{sub x} is nonstoichiometric and needs only a small amount of silver to form (x {approximately} 2--6). The structure is composed of three different clusters which are interconnected to form a three-dimensional structure. The RbGa{sub 3{minus}x}Au{sub x} system is also nonstoichiometric with a three-dimensional structure composed of Ga{sub 8} dodecahedra and four-bonded gallium atoms. Unlike Na{sub 30.5}Ga{sub 60{minus}x}Ag{sub x}, the RbGa{sub 3} binary is also stable. The binary is formally a Zintl phase but the ternary is not. Some chemistry in the alkali-metal-indium system also has been explored. A new potassium-indium binary is discussed but the structure has not been completely characterized.

  18. Low temperature recombination and trapping analysis in high purity gallium arsenide by microwave photodielectric techniques

    NASA Technical Reports Server (NTRS)

    Khambaty, M. B.; Hartwig, W. H.

    1972-01-01

    Some physical theories pertinent to the measurement properties of gallium arsenide are presented and experimental data are analyzed. A model for explaining recombination and trapping high purity gallium arsenide, valid below 77 K is assembled from points made at various places and an appraisal is given of photodielectric techniques for material property studies.

  19. Synthesis and use of (polyfluoroaryl)fluoroanions of aluminum, gallium and indium

    DOEpatents

    Marks, Tobin J. (Evanston, IL); Chen, You-Xian (Midland, MI)

    2000-01-01

    Salts of (polyfluoroaryl)fluoroanions of aluminum, gallium, and indium are described. The (polyfluoroaryl)fluoroanions have the formula [ER'R"R'"F].sup..crclbar. wherein E is aluminum, gallium, or indium, wherein F is fluorine, and wherein R', R", and R'" is each a fluorinated phenyl, fluorinated biphenyl, or fluorinated polycyclic group.

  20. Optical properties of bismuth and gallium substituted thulium iron garnet films

    Microsoft Academic Search

    R. Gerhardt; S. Sure; H. Dötsch; T. Linkewitz; W. Tolksdorf

    1993-01-01

    Bismuth and gallium substituted films of thulium iron garnet, grown by liquid phase epitaxy on [111] oriented substrates of gadolinium gallium garnet, are investigated for optical isolator applications. At a wavelength of lambda = 1.3 mum the optical damping, the refractive index, the optical anisotropy, and the Faraday rotation are measured as function of the substitution level. It turns out

  1. Diffusion of indium and gallium in Cu(In,Ga)Se2 thin film solar cells

    E-print Network

    Rockett, Angus

    Diffusion of indium and gallium in Cu(In,Ga)Se2 thin film solar cells O. Lundberga,*, J. Lua , A Abstract The diffusion of indium and gallium in polycrystalline thin film Cu(In,Ga)Se2 layers has been with energy dispersive X-ray spectroscopy. It was found that the grain boundary diffusion

  2. The development and implementation of industrial hydrometallurgical gallium recovery of the Clarksville Refinery waste residue

    NASA Astrophysics Data System (ADS)

    Fayram, Todd S.

    Todd Fayram, the Gordonsville Operation of Pasminco US Inc., and the Center for Advanced Mineral and Metallurgical Processing (CAMP) at Montana Tech studied, developed and implemented a pilot scale hydrometallurgical facility for the industrial recovery of gallium. This thesis describes the testing and engineering program that culminated in this successful recovery of gallium through process described herein.

  3. X-ray microscopy studies on the pharmaco-dynamics of therapeutic gallium in rat bones

    SciTech Connect

    Bockman, R.; Repo, M.; Warrell, R.; Pounds, J.G.; Kwiatek, W.M.; Long, G.J.; Schidlovksy, G.; Jones, K.W.

    1987-01-01

    We describe here our preliminary results on gallium and calcium quantitation and localization using x-ray microscopy techniques at the X-26 beam line of the National Synchrotron Light Source (NSLS) at 50 to 100 ..mu..m resolution and 10/sup )minus/6) gg detection levels. Since the original observation of exogenous gallium accumulation in bones, several studies have demonstrated that gallium nitrate is extremely effective in preserving boen mienral content both in vivo and in vitro. Gallium nitrate therapy normalized serum calcium levels in a study of patients with caner-related hypercalcemia, resistant to standard hydration and diuretic therapy. Recently, gallium nitrate treatment has been shown to halt the accelerated bone resorption that is frequently associated with cancers metastatic to bone. Several lines of evidence from vitro studies recently led to the demonstration of increased bone calcium and improvement in hydroxyapatite crystallinity in adult gallium-treated rats. Evidence is rapidly accumulating that gallium nitrate is an effective, new therapeutic agent for inhibition of accelerated bone resorption associated with cancer-related hypercalcemia. It has also been suggested that gallium could have wide clinical applications in disorders characterized by accelerated calcium loss from bone. 7 refs., 3 figs., 1 tab

  4. Realization of the triple points of gallium, water and mercury by an adiabatic calorimetric method

    Microsoft Academic Search

    H. Sakurai

    1996-01-01

    The triple points of water, mercury and gallium are realized, mainly for the calibration of capsule-type thermometers, by a calorimetric method using platinum cells for water and mercury, and a small glass cell for gallium. Their molar impurities are estimated from the relation between the melting temperatures and the inverses of the fraction of melt. Almost all the samples show

  5. Potential use of gallium-doped phosphate-based glass material for periodontitis treatment.

    PubMed

    Sahdev, Rohan; Ansari, Tahera I; Higham, Susan M; Valappil, Sabeel P

    2015-07-01

    This study aimed at evaluating the potential effect of gallium-incorporated phosphate-based glasses towards periodontitis-associated bacteria, Porphyromonas gingivalis, and matrix metalloproteinase-13. Periodontitis describes a group of inflammatory diseases of the gingiva and supporting structures of the periodontium. They are initiated by the accumulation of plaque bacteria, such as the putative periodontal pathogen Porphyromonas gingivalis, but the host immune response such as elevated matrix metalloproteinases are the major contributing factor for destruction of periodontal tissues. Antibacterial assays of gallium-incorporated phosphate-based glasses were conducted on Porphyromonas gingivalis ATCC 33277 using disc diffusion assay on fastidious anaerobe agar and liquid broth assay in a modified tryptic soy broth. In vitro study investigated the effect of gallium on purified recombinant human matrix metalloproteinase-13 activity using matrix metalloproteinase assay kit. In vivo biocompatibility of gallium-incorporated phosphate-based glass was evaluated in rats as subcutaneous implants. Antibacterial assay of gallium displayed activity against Porphyromonas gingivalis (inhibition zone of 22?±?0.5?mm compared with 0?mm for control glass, c-PBG). Gallium in the glass contributed to growth inhibitory effect on Porphyromonas gingivalis (up to 1.30 reductions in log?10 values of the viable counts compared with control) in a modified tryptic soy broth. In vitro study showed gallium-incorporated phosphate-based glasses inhibited matrix metalloproteinase activity significantly (p???0.01) compared with c-PBG. Evaluation of in vivo biocompatibility of gallium-incorporated phosphate-based glasses in rats showed a non-toxic and foreign body response after 2 weeks of implantation. The results indicate that gallium ions might act on multiple targets of biological mechanisms underlying periodontal disease. Moreover, gallium-incorporated phosphate-based glasses are biocompatible in a rat model. The findings warrant further investigation and will have important clinical implications in the future treatment and management of periodontitis. PMID:25681404

  6. VAl Alloy

    NASA Astrophysics Data System (ADS)

    Mikami, M.; Mizoshiri, M.; Ozaki, K.; Takazawa, H.; Yamamoto, A.; Terazawa, Y.; Takeuchi, T.

    2014-06-01

    Power generation performance of a thermoelectric module consisting of the Heusler Fe2VAl alloy was evaluated. For construction of the module, W-doped Fe2VAl alloys were prepared using powder metallurgy process. Power generation tests of the module consisting of 18 pairs of p- n junctions were conducted on a heat source of 373-673 K in vacuum. The reduction of thermal conductivity and improvement of thermoelectric figure of merit by W-doping enhanced the conversion efficiency and the output power. High output power density of 0.7 W/cm2 was obtained by virtue of the high thermoelectric power factor of the Heusler alloy. The module exhibited good durability, and the relatively high output power was maintained after temperature cycling test in air.

  7. Survival of rabbit platelets labeled with gallium 67

    SciTech Connect

    Mazoyer, E.; Carpenter, D.; Ebbe, S.; Yano, Y.; Dalal, K.; Singh, M.; Mazoyer, B.

    1988-02-01

    The viability of rabbit platelets labeled with radioactive gallium was determined to analyze the feasibility of using platelets labeled with gallium 67 as an imaging reagent for positron emission tomography. Platelets were labeled with a complex of the longer lived gallium 67 and mercaptopyridine-N-oxide (MPO) or with sodium chromate Cr 51. Their survival after transfusion was measured. Labelling efficiency of /sup 67/Ga-MPO was 6.5% to 45.8% (26.8% +/- 2.8%) when platelets were suspended in saline solution, but was much lower (1.6% +/- 0.8%) in plasma. Platelets labeled with either radioisotope in a saline medium survived as well as platelets labeled with 51Cr in plasma. Recovery values 1 hour after transfusion and mean platelet survivals were 68.6% +/- 4.9% and 3.4 +/- 0.2 days for /sup 67/Ga in saline solution, 76.5% +/- 6.8% and 3.8 +/- 0.5 days for /sup 51/Cr in saline solution, and 73.7% +/- 7.4% and 3.6 +/- 0.5 days for /sup 51/Cr in plasma. Labeled platelet concentrates always contained extra radioactivity not firmly bound to viable platelets. A postlabeling wash in saline solution did not reduce this contamination and resulted in reduction of the number of viable platelets. The results showed that rabbit platelets labeled with /sup 67/Ga-MPO survived in the circulation as well as those labeled by a standard protocol with sodium chromate Cr 51.

  8. Self-diffusion in liquid gallium and hard sphere model

    NASA Astrophysics Data System (ADS)

    Blagoveshchenskii, Nikolay; Novikov, Arkady; Puchkov, Alexander; Savostin, Vadim; Sobolev, Oleg

    2015-01-01

    Incoherent and coherent components of quasielastic neutron scattering have been studied in the temperature range of T = 313 K - 793 K aiming to explore the applicability limits of the hard-sphere approach for the microscopic dynamics of liquid gallium, which is usually considered as a non-hard-sphere system. It was found that the non-hard-sphere effects come into play at the distances shorter than the average interatomic distance. The longer range diffusive dynamics of liquid Ga is dominated by the repulsive forces between the atoms.

  9. Gallium uptake in tryptophan-related pulmonary disease

    SciTech Connect

    Kim, S.M.; Park, C.H.; Intenzo, C.M.; Patel, R. (Thomas Jefferson Univ. Hospital, Philadelphia, PA (USA))

    1991-02-01

    We describe a patient who developed fever, fatigue, muscle weakness, dyspnea, skin rash, and eosinophilia after taking high doses of tryptophan for insomnia for two years. A gallium-67 scan revealed diffuse increased uptake in the lung and no abnormal uptake in the muscular distribution. Bronchoscopy and biopsy confirmed inflammatory reactions with infiltration by eosinophils, mast cells, and lymphocytes. CT scan showed an interstitial alveolar pattern without fibrosis. EMG demonstrated diffuse myopathy. Muscle biopsy from the right thigh showed an inflammatory myositis with eosinophilic and lymphocytic infiltrations.

  10. Testing of gallium arsenide solar cells on the CRRES vehicle

    NASA Technical Reports Server (NTRS)

    Trumble, T. M.

    1985-01-01

    A flight experiment was designed to determine the optimum design for gallium arsenide (GaAs) solar cell panels in a radiation environment. Elements of the experiment design include, different coverglass material and thicknesses, welded and soldered interconnects, different solar cell efficiencies, different solar cell types, and measurement of annealing properties. This experiment is scheduled to fly on the Combined Release and Radiation Effects Satellite (CRRES). This satellite will simultaneously measure the radiation environment and provide engineering data on solar cell degradation that can be directly related to radiation damage.

  11. Lasing action in gallium nitride quasicrystal nanorod arrays.

    PubMed

    Chang, Shih-Pang; Sou, Kuok-Pan; Chen, Chieh-Han; Cheng, Yuh-Jen; Huang, Ji-Kai; Lin, Chung-Hsiang; Kuo, Hao-Chung; Chang, Chun-Yen; Hsieh, Wen-Feng

    2012-05-21

    We report the observation of lasing action from an optically pumped gallium nitride quasicrystal nanorod arrays. The nanorods were fabricated from a GaN substrate by patterned etching, followed by epitaxial regrowth. The nanorods were arranged in a 12-fold symmetric quasicrystal pattern. The regrowth grew hexagonal crystalline facets and core-shell multiple quantum wells (MQWs) on nanorods. Under optical pumping, multiple lasing peaks resembling random lasing were observed. The lasing was identified to be from the emission of MQWs on the nanorod sidewalls. The resonant spectrum and mode field of the 12-fold symmetric photonic quasicrystal nanorod arrays is discussed. PMID:22714233

  12. Interdiffusion of magnesium and iron dopants in gallium nitride

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Tomonobu; Kitatani, Takeshi; Terano, Akihisa; Mochizuki, Kazuhiro

    2015-03-01

    The interdiffusion of magnesium and iron in gallium nitride (GaN), i.e., magnesium–iron interdiffusion, was investigated using magnesium-doped GaN layers on iron-doped GaN substrates. The investigation confirms that the magnesium–iron interdiffusion strongly depends on the concentrations of magnesium and iron, that is, it occurs when the iron and magnesium concentrations are high (magnesium: 2 × 1020 cm?3 iron: 2 × 1019 cm?3). It also confirms that diffused iron in the magnesium-doped GaN layer acts as a nonradiative recombination center in GaN.

  13. Nanocrystalline Rare Earth-doped Gallium Nitride Phosphor Powders

    Microsoft Academic Search

    G. A. Hirata; J. Tao; P. Chen; K. C. Mishra; J. McKittrick

    We report on the fabrication and luminescent properties of rare earth-doped gallium nitride (GaN) phosphor powders. Single phase GaN and GaN:RE3+ powders were prepared by using a novel chemical route. In this work a new method for the synthesis of high purity, single phase doped GaN powders is reported. (Ga1-xREx)N powders are obtained by dissolving metal nitrates (Ga(NO3)3, (RE(NO3)3) in

  14. Lasing action in gallium nitride photonic quasicrystal nanorod arrays

    NASA Astrophysics Data System (ADS)

    Chang, Shih-Pang; Sou, Kuok-Pan; Chang, Jet-Rung; Cheng, Yuh-Jen; Li, Yuh-Jing; Chen, Yi-Chen; Kuo, Hao-Chung; Hsu, Ken-Yuh; Chang, Chun-Yen

    2012-03-01

    We report the observation of lasing action from optically pumped gallium nitride nanorod arrays in a quasicrystal pattern. The nanorods were fabricated from a GaN substrate by nanoimprint patterned etching, followed by epitaxial regrowth to form crystalline facets. The imprint was a 12-fold symmetric quasicrystal pattern. The regrowth grew a multiple quantum well core-shell structure on nanorods. The cathodoluminescent emission of quantum wells red shifts from the bottom to top region of nanorod. Under optical pumping, multiple lasing peaks were observed. The lasing modes formed by 12-fold symmetric photonic quasicrystal nanorod arrays are discussed.

  15. [Experimental studies on the systemic toxicity of dental alloys free of precious metals].

    PubMed

    Reuling, N; Fuhrmann, R; Keil, M

    1992-01-01

    The systemic toxicity of five non-precious dental alloys was evaluated by help of an animal study. The pulverized dental alloys, filled in gelatine capsules, were orally administered to laboratory rats using a special esophageal application device. For each alloy examined randomized groups of ten experimental animals and ten control animals were used. For a period of seven days the experimental animals received daily 1000 mg alloy powder per kilogram body-weight. The animals of the control groups received daily empty gelatine capsules (placebo application). After two weeks all animals were killed and autopsies of the animals were performed. Histopathologic examinations of the lungs, kidneys, liver, small intestine and large intestine of all animals were done. With statistic significance (p less than 0.001) rats whom nickel-chromium alloys were administered orally showed serious pathologic reactions more frequently than placebo-treated control animals. Nickel-chromium alloys containing beryllium and/or gallium caused the strongest organic lesions. In contrary to this a dental cobalt-chromium alloy showed a very low systemic toxicity. The results of the study underline that preclinical toxicity testing of dental alloys is necessary in order to avoid systemic toxic lesions in man. PMID:1496349

  16. Electrodeposition of crystalline GaAs on liquid gallium electrodes in aqueous electrolytes.

    PubMed

    Fahrenkrug, Eli; Gu, Junsi; Maldonado, Stephen

    2013-01-01

    Crystalline GaAs (c-GaAs) has been prepared directly through electroreduction of As(2)O(3) dissolved in an alkaline aqueous solution at a liquid gallium (Ga(l)) electrode at modest temperatures (T ? 80 °C). Ga(l) pool electrodes yielded consistent electrochemical behavior, affording repetitive measurements that illustrated the interdependences of applied potential, concentration of dissolved As(2)O(3), and electrodeposition temperature on the quality of the resultant c-GaAs(s). Raman spectra indicated the composition of the resultant film was strongly dependent on both the electrodeposition temperature and dissolved concentration of As(2)O(3) but not to the applied bias. For electrodepositions performed either at room temperature or with high (?0.01 M) concentrations of dissolved As(2)O(3), Raman spectra of the electrodeposited films were consistent with amorphous As(s). X-ray diffractograms of As(s) films collected after thermal annealing indicated metallurgical alloying occurred only at temperatures in excess of 200 °C. Optical images and Raman spectra separately showed the composition of the as-electrodeposited film in dilute (?0.001 M) solutions of dissolved As(2)O(3)(aq) was pure c-GaAs(s) at much lower temperatures than 200 °C. Diffractograms and transmission electron microscopy performed on as-prepared films confirmed the identity of c-GaAs(s). The collective results thus provide the first clear demonstration of an electrochemical liquid-liquid-solid (ec-LLS) process involving a liquid metal that serves simultaneously as an electrode, a solvent/medium for crystal growth, and a coreactant for the synthesis of a polycrystalline semiconductor. The presented data serve as impetus for the further development of the ec-LLS process as a controllable, simple, and direct route for technologically important optoelectronic materials such as c-GaAs(s). PMID:23265429

  17. Iron-Targeting Antitumor Activity of Gallium Compounds and Novel Insights Into Triapine®-Metal Complexes

    PubMed Central

    Antholine, William E.

    2013-01-01

    Abstract Significance: Despite advances made in the treatment of cancer, a significant number of patients succumb to this disease every year. Hence, there is a great need to develop new anticancer agents. Recent Advances: Emerging data show that malignant cells have a greater requirement for iron than normal cells do and that proteins involved in iron import, export, and storage may be altered in cancer cells. Therefore, strategies to perturb these iron-dependent steps in malignant cells hold promise for the treatment of cancer. Recent studies show that gallium compounds and metal-thiosemicarbazone complexes inhibit tumor cell growth by targeting iron homeostasis, including iron-dependent ribonucleotide reductase. Chemical similarities of gallium(III) with iron(III) enable the former to mimic the latter and interpose itself in critical iron-dependent steps in cellular proliferation. Newer gallium compounds have emerged with additional mechanisms of action. In clinical trials, the first-generation-compound gallium nitrate has exhibited activity against bladder cancer and non-Hodgkin's lymphoma, while the thiosemicarbazone Triapine® has demonstrated activity against other tumors. Critical Issues: Novel gallium compounds with greater cytotoxicity and a broader spectrum of antineoplastic activity than gallium nitrate should continue to be developed. Future Directions: The antineoplastic activity and toxicity of the existing novel gallium compounds and thiosemicarbazone-metal complexes should be tested in animal tumor models and advanced to Phase I and II clinical trials. Future research should identify biologic markers that predict tumor sensitivity to gallium compounds. This will help direct gallium-based therapy to cancer patients who are most likely to benefit from it. Antioxid. Redox Signal. 00, 000–000. PMID:22900955

  18. High-surface Thermally Stable Mesoporous Gallium Phosphates Constituted by Nanoparticles as Primary Building Blocks

    SciTech Connect

    V Parvulescu; V Parvulescu; D Ciuparu; C Hardacre; H Garcia

    2011-12-31

    In constant, search for micro/mesoporous materials, gallium phosphates, have attracted continued interest due to the large pore size reported for some of these solids in comparison with analogous aluminum phosphates. However up to now, the porosity of gallium phosphates collapsed upon template removal or exposure to the ambient moisture. In the present work, we describe high-surface thermally stable mesoporous gallium phosphates synthesized from gallium propoxide and PCl{sub 3} and different templating agents such as amines (dipropylamine, piperidine and aminopiperidine) and quaternary ammonium salts (C{sub 16}H{sub 33}(CH{sub 3})3NBr and C{sub 16}PyCl). These highly reactive precursors have so far not been used as gallium and phosphate sources for the synthesis of gallophosphates. Conceptually, our present synthetic procedure is based on the fast formation of gallium phosphate nanoparticles via the reaction of gallium propoxide with PCl{sub 3} and subsequent construction of the porous material with nanoparticles as building blocks. The organization of the gallophosphate nanoparticles in stable porous structures is effected by the templates. Different experimental procedures varying the molar composition of the sol-gel, pH and the pretreatment of gallium precursor were assayed, most of them leading to satisfactory materials in terms of thermal stability and porosity. In this way, a series of gallium phosphates with surface are above 200 m{sup 2} g{sup -1}, and narrow pore size from 3 to 6 nm and remarkable thermal stability (up to 550 C) have been prepared. In some cases, the structure tends to show some periodicity and regularity as determined by XRD. The remarkable stability has allowed us to test the catalytic activity of gallophosphates for the aerobic oxidation of alkylaromatics with notable good results. Our report reopens the interest for gallophosphates in heterogeneous catalysis.

  19. Experimental investigation of electron transport properties of gallium nitride nanowires

    NASA Astrophysics Data System (ADS)

    Motayed, Abhishek; Davydov, Albert V.; Mohammad, S. N.; Melngailis, John

    2008-07-01

    We report transport properties of gallium nitride (GaN) nanowires grown using direct reaction of ammonia and gallium vapor. Reliable devices, such as four-terminal resistivity measuring structures and field-effect transistors, were realized by dielectrophoretically aligning the nanowires on an oxidized silicon substrate and subsequently applying standard microfabrication techniques. Room-temperature resistivity in the range of (1.0-6.2)×10-2 ? cm was obtained for the nanowires with diameters ranging from 200 to 90 nm. Temperature-dependent resistivity and mobility measurements indicated the possible sources for the n-type conductivity and high background charge carrier concentration in these nanowires. Specific contact resistance in the range of 5.0×10-5 ? cm2 was extracted for Ti/Al/Ti/Au metal contacts to GaN nanowires. Significant reduction in the activation energy of the dopants at low temperatures (<200 K) was observed in the temperature-dependent resistivity measurement of these nanowires, which is linked to the onset of degeneracy. Temperature-dependent field-effect mobility measurements indicated that the ionized impurity scattering is the dominant mechanism in these nanowires at all temperatures.

  20. Electrical characterisation of magnesium and tellurium implanted indium gallium arsenide

    SciTech Connect

    Gwilliam, R.M.; Sealy, B.J.; Mynard, J.E. [Univ. of Surrey, Guildford (United Kingdom)] [and others

    1996-12-31

    There has been a great deal of interest in the Indium Gallium Arsenide (InGaAs) material system, both lattice matched to Indium Phosphide (InP) as well as material grown pseudomorphically on GaAs because of its importance to optoelectronic devices. In this paper we present some preliminary observations on the electrical properties of In{sub x}Ga{sub 1-x}As on Gallium Arsenide (GaAs) substrate implanted with magnesium with x varying between 0 to 60 atomic %. Our results indicate that p-type activity is difficult to realise in In{sub x}Ga{sub 1-x}As for x > 50%. We also report results of tellurium doubly charged implanted into In{sub 0.53}Ga{sub 0.47}As lattice matched to InP. About 600 angstroms of rf sputtered Aluminum Nitride (AIN) encapsulant was used to carry out 30s isochronal anneals in an optical furnace at temperatures of 600, 700 and 800{degrees}C. Differential Hall effect measurements were performed to provide dopant depth profiles. Good dopant activation and mobilities were obtained.

  1. Gallium phosphide high-temperature bipolar junction transistor

    SciTech Connect

    Zipperian, T.E.; Dawson, L.R.; Caffin, R.J.

    1981-03-01

    Preliminary results are reported on the development of a high-temperature (> 350/sup 0/C) gallium phosphide bipolar junction transistor (BJT) for goethermal and other energy applications. This four-layer p/sup +/n/sup -/pp/sup +/ structure was fromed by liquid phase epitaxy using a supercooling technique to insure uniform nucleation of the thin layers. Magnesium was used as the p-type dopant to avoid excessive out-diffusion into the lightly doped base. By appropriate choice of electrodes, the device may also be driven as an n-channel junction field-effect transistor. The gallium phosphide BJT is observed to have a common-emitter current gain peaking in the range of 6 to 10 (for temperatures from 20/sup 0/C to 400/sup 0/C) and a room-temperature, punchthrough-limited, collector-emitter breakdown voltage of approximately -6V. Other parameters of interest include an f/sub/ = 400 KHz (at 20/sup 0/C) and a collector base leakage current = 200 ..mu..A (at 350/sup 0/C).

  2. Crystallographic alignment of high-density gallium nitride nanowire arrays.

    PubMed

    Kuykendall, Tevye; Pauzauskie, Peter J; Zhang, Yanfeng; Goldberger, Joshua; Sirbuly, Donald; Denlinger, Jonathan; Yang, Peidong

    2004-08-01

    Single-crystalline, one-dimensional semiconductor nanostructures are considered to be one of the critical building blocks for nanoscale optoelectronics. Elucidation of the vapour-liquid-solid growth mechanism has already enabled precise control over nanowire position and size, yet to date, no reports have demonstrated the ability to choose from different crystallographic growth directions of a nanowire array. Control over the nanowire growth direction is extremely desirable, in that anisotropic parameters such as thermal and electrical conductivity, index of refraction, piezoelectric polarization, and bandgap may be used to tune the physical properties of nanowires made from a given material. Here we demonstrate the use of metal-organic chemical vapour deposition (MOCVD) and appropriate substrate selection to control the crystallographic growth directions of high-density arrays of gallium nitride nanowires with distinct geometric and physical properties. Epitaxial growth of wurtzite gallium nitride on (100) gamma-LiAlO(2) and (111) MgO single-crystal substrates resulted in the selective growth of nanowires in the orthogonal [1\\[Evec]0] and [001] directions, exhibiting triangular and hexagonal cross-sections and drastically different optical emission. The MOCVD process is entirely compatible with the current GaN thin-film technology, which would lead to easy scale-up and device integration. PMID:15273744

  3. Gallium-67 imaging in retroperitoneal fibrosis: Significance of a negative result

    SciTech Connect

    Jacobson, A.F. (Department of Veterans Affairs Medical Center, Seattle, WA (USA))

    1991-03-01

    A patient with retroperitoneal fibrosis and right peritracheal and hilar lymphadenopathy was studied using gallium-67-citrate. No abnormal uptake was seen in the regions of retroperitoneal fibrosis, while there was avid uptake in chest lesions later shown to represent small cell lung carcinoma. Retroperitoneal fibrosis which does not show gallium uptake is most likely mature, with few inflammatory elements. In patients with multiple retroperitoneal and/or mediastinal masses, gallium imaging may be useful in identifying the most active sites of disease for possible biopsy and for subsequent monitoring of response to therapy.

  4. Gallium scintigraphy for diagnosis of septic arthritis and osteomyelitis in children

    SciTech Connect

    Borman, T.R.; Johnson, R.A.; Sherman, F.C.

    1986-05-01

    Thirty-four children with presumptive acute osteomyelitis or septic arthritis underwent early gallium-67 citrate scintigraphy and have been retrospectively reviewed. Diagnostic accuracy using this technique was 91%. Gallium-67 citrate is a more reliable radiopharmaceutical agent for the detection of selected acute musculoskeletal infections than either technetium methylene diphosphonate or indium-111. However, the radiation dosage from gallium is higher than from other radiopharmaceutical agents, and the authors would recommend its use only in cases where the diagnosis cannot be made on the basis of clinical, laboratory, or plain roentgenographic criteria.

  5. Wurtzite Gallium Nitride as a scintillator detector for alpha particles (a Geant4 simulation)

    NASA Astrophysics Data System (ADS)

    Taheri, A.; Sheidaiy, M.

    2015-05-01

    Gallium Nitride has become a very popular material in electronics and optoelectronics. Because of its interesting properties, it is suitable for a large range of applications. This material also shows very good scintillation properties that make it a possible candidate for use as a charged particles scintillator detector. In this work, we simulated the scintillation and optical properties of the gallium nitride in the presence of alpha particles using Geant4. The results show that gallium nitride can be an appropriate choice for this purpose.

  6. Concerning the energy levels of silver in Ge-Si alloys

    SciTech Connect

    Tahirov, V. I. [Baku State University (Azerbaijan); Agamaliev, Z. A. [National Academy of Sciences of Azerbaijan, Institute of Physics (Azerbaijan); Sadixova, S. R.; Guliev, A. F.; Gahramanov, N. F., E-mail: n_gakhramanov@mail.ru [Sumgait State University (Azerbaijan)

    2012-03-15

    The emission from impurity states of silver (an element of the IB subgroup) in a Ge-Si alloy, containing 18 at % Si, has been studied. The donor level of silver has been found in crystals doubly doped with gallium and silver, while its first acceptor level has been revealed in crystals doped with only silver. Single crystals were grown by pulling from a melt using a feeding rod. Doping with gallium was performed by introducing this element into the feeding rod, and silver was introduced into the crystals via diffusion. The positions of the donor and first acceptor Ag levels with respect to the top of the valence band were found by analyzing the temperature dependence of the Hall coefficient and the electroneutrality equation for the crystal: 0.06 and 0.29 eV, respectively.

  7. Real-time in-situ chemical sensing in aluminum gallium nitride/gallium nitride metal-organic chemical vapor deposition processes for advanced process control

    NASA Astrophysics Data System (ADS)

    Cho, Soon

    Gallium nitride and its alloys promise to be key materials for future semiconductor devices aimed at high frequency, high power electronic applications. However, manufacturing for such high performance products is challenged by reproducibility and material quality constraints that are notably more stringent than those required for optoelectronic applications. To meet this challenge, in-situ mass spectrometry was implemented as a real-time process- and wafer-state metrology tool in AlGaN/GaN/AlN metal-organic chemical vapor deposition processes on semi-insulating SiC substrate wafers. Dynamic chemical sensing through the process cycle, carried out downstream from the wafer, revealed generation of methane and ethane reaction byproducts, as well as other residual gas species. Real-time metrics were derived based on the chemical signals to predict/control material quality and thickness of critical layers within the heterostructure in real time during growth, and corresponding metrologies were used for real-time advanced process control. Using the methane/ethane ratio, GaN epilayer crystal quality was predicted in real time to 2--5% precision, which was verified by post-process x-ray diffraction. Moreover, the same real-time metric predicted material quality as indicated by post-process photoluminescence band-edge intensities to ˜5% precision. The methane/ethane ratio has a fundamental significance in terms of the intrinsic chemistry in that the two byproducts are believed to reflect two parallel reaction pathways leading to GaN-based material growth, namely the gas phase adduct formation route and the surface route for direct precursor decomposition, respectively. The fact that lower methane/ethane ratios consistently yield better material quality suggests that the surface pathway is preferred for high quality GaN growth. In addition, a metric based on methane and ethane signals integrated through the AlGaN growth period (˜1 min or less) enabled prediction of the cap layer thickness (˜20 nm) to within ˜1% precision, which was verified by post-process x-ray reflectance. These types of real-time advanced process control activities in terms of fault detection and management, course correction, and pre-growth contamination control have made significant contributions to the GaN-based semiconductor development and manufacturing at Northrop Grumman Electronics Systems in terms of improved material quality, yield, and consequent cost reduction, and they are now in routine use.

  8. Growth and characterization of gallium indium nitrogen arsenide and gallium indium nitrogen phosphide

    NASA Astrophysics Data System (ADS)

    Hong, Yuguang

    Nitrogen incorporation into GaInAs and GaInP based on GaAs (100) substrates has attracted a great deal of attention due to their potential applications in ultra-high-efficiency multijunction solar cells as well as in optoelectronic devices. In order to investigate not yet well-studied material families of III-N-V compounds, we use gas-source molecule beam epitaxy (MBE) method, in which nitrogen radicals are used as the nitrogen precursor, to grow mixed group-V nitride alloy semiconductors with excellent crystallinity. This dissertation is divided into two major parts. In the first part, we use different structures to improve GaInNAs material quality, including strain-compensated GaIn0.08As/GaN0.03As and strained InAs/GaN0.03As0.97 short-period superlattices (SPSLs). The photoluminescence intensity of the SPSLs is 12 times higher than that of random alloys, while electron mobility is improved by a factor of two. InAs/GaN0.03As0.97 SPSL is very promising for 1.3 mum GaInNAs quantum well laser application. Photoconductance measurements show a type-II band lineup for the Ga0.92In0.08As/GaN 0.03As0.97 heterojunction. In the second part, we demonstrate the successful growth of a novel material, GaInNP. Fundamental optical and electrical transport properties of GaInNP are studied. Nitrogen incorporation dramatically reduces the GalnP band gap, which can be successfully explained by the band anticrossing model based on the concept of an anticrossing interaction between localized N states and the extended conduction band states. Rapid thermal annealing improves the optical properties, but decreases the free electron concentration because Si dopant is passivated by N through the formation of Si-N pairs. Band alignment between GaInNP and GaAs is also investigated. GaInNP is an ideal material for tunnel-collector heterojunction bipolar transistors (HBTs). In comparing the properties of GaInNP and GaInNAs, great similarities are found in terms of the effect of nitrogen incorporation. Here, the band anticrossing model successfully explains the band gap reduction and predicts an increase of the electron effective mass for both material.

  9. Renal gallium accumulation in the absence of renal pathology in patients with severe hepatocellular disease

    SciTech Connect

    Alazraki, N.; Sterkel, B.; Taylor, A. Jr.

    1983-05-01

    Visualization of Ga-67 citrate in the kidneys at 48 hours and 72 hours post injection is usually interpreted as evidence of renal pathology. In reviewing approximately 200 consecutive patients referred for gallium scans, 40 patients who also underwent liver/spleen Tc-99m sulfur colloid (SC) studies within one month of the gallium study were identified. Fourteen of these patients showed advanced hepatocellular dysfunction on the Tc-99m SC liver/spleen images. Of these 14 patients, nine had persistent renal accumulation of gallium at 48 or 72 hours. Five of these nine patients had no evidence of primary renal disease by clinical or postmortem examination and subsequent clinical information indicated that two additional patients probably had no significant renal pathology. Therefore, bilateral symmetrically increased renal uptake of gallium in patients with advanced hepatocellular disease should not necessarily be interpreted as evidence of renal pathology.

  10. Gallium-67 scintigraphy, bronchoalveolar lavage, and pathologic changes in patients with pulmonary sarcoidosis

    SciTech Connect

    Abe, S.; Munakata, M.; Nishimura, M.; Tsuneta, Y.; Terai, T.; Nakano, I.; Ohsaki, Y.; Kawakami, Y.

    1984-05-01

    The intensity of gallium-67 scintiscans, lymphocyte counts in bronchoalveolar lavage fluid, and pathologic changes were studied in 26 patients with untreated pulmonary sarcoidosis. Noncaseating granulomas were recognized with significantly greater frequency in stage 2 (80 percent; 8/10 cases) than in stage 1 (43 percent; 6/14 cases). Alveolitis showed little relation to the roentgenographic stage. There was a strong correlation between the intensity of gallium uptake in pulmonary parenchyma and the detection rate of granuloma; however, the detection rate of alveolitis was not statistically different from the intensity of gallium uptake. A highly significant correlation was revealed between the lymphocyte counts in bronchoalveolar lavage fluid and the intensity of alveolitis. These observations suggest that the gallium uptake reflects mainly the presence of granuloma, and the lymphocyte count in bronchoalveolar lavage fluid reflects the intensity of alveolitis in patients with pulmonary sarcoidosis.

  11. Gallium nitride (GaN) HEMT's: progress and potential for commercial applications

    Microsoft Academic Search

    J. Shealy; J. Smart; M. Poulton; R. Sadler; D. Grider; S. Gibb; B. Hosse; B. Sousa; D. Halchin; V. Steel; P. Garber; P. Wilkerson; B. Zaroff; J. Dick; T. Mercier; J. Bonaker; C. Greer; M. Isenhour

    2002-01-01

    This paper focuses on the development of 100 mm gallium nitride HEMT technology at RF Micro Devices and the utilization of GaN transistors for commercial applications such as power amplifiers, power switches and low-noise power oscillators.

  12. Anomalous dynamics of the residual voltage across a gallium-arsenide diode upon subnanosecond avalanche switching

    NASA Astrophysics Data System (ADS)

    Brylevskii, V. I.; Rozhkov, A. V.; Smirnova, I. A.; Rodin, P. B.; Grekhov, I. V.

    2015-04-01

    A qualitative difference between high-voltage gallium-arsenide diodes and similar silicon devices is found experimentally upon ultrafast switching in the delayed avalanche breakdown regime. It is shown that, following switching, a gallium-arsenide diode remains in a highly conductive state throughout the entire duration of the applied voltage pulse and the recovery of the reverse voltage across the p- n junction due to the dispersal of nonequilibrium electron-hole plasma is not observed. In the same interval of time (2 ns in our experiment), a silicon diode passes completely into a blocking state. The residual voltage amplitude for a gallium-arsenide diode is an order of magnitude lower than that for a silicon device. The discovered effect is similar to a known effect of "sticking" of gallium-arsenide diode switches (the lock-on effect), which are triggered by a laser pulse, in a conductive state.

  13. Influence of neodymium concentration on excitation and emission properties of Nd doped gallium oxide nanocrystalline films

    NASA Astrophysics Data System (ADS)

    Podhorodecki, A.; Banski, M.; Misiewicz, J.; Lecerf, C.; Marie, P.; Cardin, J.; Portier, X.

    2010-09-01

    Gallium oxide and more particularly ?-Ga2O3 matrix is an excellent material for new generation of devices electrically or optically driven as it is known as the widest band gap transparent conductive oxide. In this paper, the optical properties of neodymium doped gallium oxide films grown by magnetron sputtering have been analyzed. The influence of the Nd ions concentration on the excitation/emission mechanisms of Nd ions and the role of gallium oxide matrix have been investigated. The grain size reduction into gallium oxide films have been observed when concentration of Nd increases. It has been found for all samples that the charge transfer is the main excitation mechanism for Nd ions where defect states play an important role as intermediate states. As a consequence Nd emission efficiency increases with temperature giving rise to most intensive emission at 1087 nm at room temperature.

  14. Journal of Crystal Growth 274 (2005) 1420 Growth and characterization of single-crystalline gallium

    E-print Network

    Anderson, Timothy J.

    2005-01-01

    is gallium nitride, with which blue and ultraviolet light-emitting diodes and lasers are produced. Mostly;coefficients and lattice constants to reduce the stresses of heteroepitaxy with GaN. Lithium aluminum oxide

  15. Measurement of Quantized Conductance in Gallium Using a Scanning Tunneling Microscope

    NASA Astrophysics Data System (ADS)

    Lewis, B. B.; Vandervoort, K. G.

    1998-03-01

    A scanning tunneling microscope was employed to form nanometer diameter wires in gallium in various states. Nanowires form when objects come in and out of contact, much like the filaments that form when you step on a piece of gum and pull your foot away. When nanowires form, quantized steps in conductance occur and can be measured. The low melting point of gallium was utilized to study the quantized conductance dependence on the physical state of the metal. For temperatures adequately below gallium's melting point, quantized effects are seen that correspond to other studies performed on gold, copper, and aluminum. At temperatures near the melting point of gallium, there appears to be a weaker quantum effect. By varying the type of STM tip, the dependence on the contact metal was observed. Statistical analysis of conductance steps was performed and will be discussed.

  16. Gallium Content in PuO{sub 2} Using Laser Induced Breakdown Spectroscopy (LIBS)

    SciTech Connect

    Smith, C.A.; Martinez, M.A.; Veirs, D.K.

    1999-08-29

    Laser Induced Breakdown Spectroscopy (LIBS) has been applied to the semi-quantitative analysis of gallium in plutonium oxide at the Los Alamos Plutonium Facility. The oxide samples were generated by the Thermally Induced Gallium Removal (TIGR) process, a pretreatment step prior to MOX fuel processing. The TIGR process uses PuO{sub 2} containing 1 wt% gallium (nominal) as feed material. Following the TIGR process, gallium content was analyzed by LIBS and also by conventional wet chemical analysis (ICP-MS). Although the data range was insufficient to obtain an adequate calibration, general agreement between the two techniques was good. LIBS was found to have a useful analytical range of 34-400 ppm for Ga in PuO{sub 2}.

  17. Morphology, mechanical stability, and protective properties of ultrathin gallium oxide coatings.

    PubMed

    Lawrenz, Frank; Lange, Philipp; Severin, Nikolai; Rabe, Jürgen P; Helm, Christiane A; Block, Stephan

    2015-06-01

    Ultrathin gallium oxide layers with a thickness of 2.8 ± 0.2 nm were transferred from the surface of liquid gallium onto solid substrates, including conjugated polymer poly(3-hexylthiophene) (P3HT). The gallium oxide exhibits high mechanical stability, withstanding normal pressures of up to 1 GPa in contact mode scanning force microscopy imaging. Moreover, it lowers the rate of photodegradation of P3HT by 4 orders of magnitude, as compared to uncovered P3HT. This allows us to estimate the upper limits for oxygen and water vapor transmission rates of 0.08 cm(3) m(-2) day(-1) and 0.06 mg m(-2) day(-1), respectively. Hence, similar to other highly functional coatings such as graphene, ultrathin gallium oxide layers can be regarded as promising candidates for protective layers in flexible organic (opto-)electronics and photovoltaics because they offer permeation barrier functionalities in conjunction with high optical transparency. PMID:25945521

  18. Influence of neodymium concentration on excitation and emission properties of Nd doped gallium oxide nanocrystalline films

    SciTech Connect

    Podhorodecki, A.; Banski, M.; Misiewicz, J. [Institute of Physics, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland); Lecerf, C.; Marie, P.; Cardin, J.; Portier, X. [CIMAP, CEA/UMR CNRS 6252/ENSICAEN, Universite de Caen Basse Normandie, 6 Boulevard Marechal Juin, 14050 Caen (France)

    2010-09-15

    Gallium oxide and more particularly {beta}-Ga{sub 2}O{sub 3} matrix is an excellent material for new generation of devices electrically or optically driven as it is known as the widest band gap transparent conductive oxide. In this paper, the optical properties of neodymium doped gallium oxide films grown by magnetron sputtering have been analyzed. The influence of the Nd ions concentration on the excitation/emission mechanisms of Nd ions and the role of gallium oxide matrix have been investigated. The grain size reduction into gallium oxide films have been observed when concentration of Nd increases. It has been found for all samples that the charge transfer is the main excitation mechanism for Nd ions where defect states play an important role as intermediate states. As a consequence Nd emission efficiency increases with temperature giving rise to most intensive emission at 1087 nm at room temperature.

  19. Process for producing gallium-containing solution from the aluminum smelting dust

    SciTech Connect

    Era, A.; Matsui, S.; Ikeda, H.

    1988-03-01

    A process is described for producing a gallium-containing solution from aluminum smelting dust comprising leaching aluminum smelting dust with a mineral acid selected from the group consisting of sulfuric acid, hydrochloric acid and nitric acid, and adding an oxidizing agent to the aluminum smelting dust at the time of leaching to preferentially leach and extract gallium from the aluminum smelting dust without extracting aluminum from the aluminum smelting dust. The oxidizing agent is selected from the group consisting of potassium permanganate, manganese dioxide, hydrogen peroxide, ozone, potassium chromate, potassium dichromate, ammonium persulfate, sodium hydrochlorite, sodium chlorite and sodium chlorate. The leached aluminum smelting dust is filtered to obtain a gallium-containing solution of dissolved gallium.

  20. Ultrasonic cavitation of molten gallium: formation of micro- and nano-spheres.

    PubMed

    Kumar, Vijay Bhooshan; Gedanken, Aharon; Kimmel, Giora; Porat, Ze'ev

    2014-05-01

    Pure gallium has a low melting point (29.8°C) and can be melted in warm water or organic liquids, thus forming two immiscible liquid phases. Irradiation of this system with ultrasonic energy causes cavitation and dispersion of the molten gallium as microscopic spheres. The resultant spheres were found to have radii range of 0.2-5 ?m and they do not coalesce upon cessation of irradiation, although the ambient temperature is well above the m.p. of gallium. It was found that the spheres formed in water are covered with crystallites of GaO(OH), whereas those formed in organic liquids (hexane and n-dodecane) are smooth, lacking such crystallites. However, Raman spectroscopy revealed that the spheres formed in organic liquids are coated with a carbon film. The latter may be the factor preventing their coalescence at temperatures above the m.p. of gallium. PMID:24296070

  1. Development and characterization of ohmic and Schottky contacts for gallium nitride and aluminum gallium nitride devices

    NASA Astrophysics Data System (ADS)

    Zhou, Ling

    Currently, there is strong interest in the development of III-N-based field effect transistors for microwave, high-power, and high-temperature applications. The AlGaN/GaN system is well suited for these applications due to their high electron drift velocities, high breakdown fields, and relatively good thermal conductivities. The chemical stability and mechanical hardness of the nitrides also afford these devices the latitude of operating in harsh environments. The direct energy gap of III-nitrides and their alloys also make them ideal candidates for optoelectronic devices, especially for emitters and detectors working in the green to deep-UV region of the electromagnetic spectrum. Schottky and ohmic contacts are essential building blocks for both electronic and optoelectronic devices. Due to the recent emergence of the III-N materials, contacts to these materials are poorly characterized and understood. In this work, the development and the characterization of electrical and materials performance of these contacts are presented. Various ohmic contact schemes on p-type GaN, n-type GaN and AlGaN, as well as Schottky contacts on GaN and AlGaN were studied using a wide range of electrical and materials characterization techniques. Band gap engineering and purely process-oriented techniques such as annealing, wet and dry etching were used to improve the electrical characteristics of these contacts. Materials analyses were used to understand the evolution of electrical behavior of these contacts at higher temperatures.

  2. Forward-biased current annealing of radiation damaged gallium arsenide and silicon solar cells

    Microsoft Academic Search

    Richard L. Staats

    1987-01-01

    Radiation damaged gallium arsenide and silicon solar cells were annealed using a combination of thermal and Forward-bias Current Annealing techniques. These cells were annealed under varying current densities from 0.125 A\\/sq cm to 1.250 A\\/sq cm and at temperatures from 90 C to 140 C. Gallium arsenide solar cells annealed at current densities from 0.250 A\\/sq cm to 0.750 A\\/sq

  3. Straw man trade between multi-junction, gallium arsenide, and silicon solar cells

    Microsoft Academic Search

    Edward M. Gaddy

    1995-01-01

    Multi-junction (MJ), gallium arsenide (GaAs), and silicon (Si) solar cells have respective test efficiencies of approximately 24%, 18.5% and 14.8%. Multi-junction and gallium arsenide solar cells weigh more than silicon solar cells and cost approximately five times as much per unit power at the cell level. A straw man trade is performed for the TRMM spacecraft to determine which of

  4. Haemophilus parainfluenzae bacteremia associated with a pacemaker wire localized by gallium scan

    SciTech Connect

    Rosenbaum, G.S.; Calubiran, O.; Cunha, B.A. (Winthrop-Univ. Hospital, Mineola, NY (USA))

    1990-05-01

    A young woman with a history of sick sinus syndrome and placement of a permanent pacemaker 6 months before admission had fever and Haemophilus parainfluenzae bacteremia. A gallium scan localized the infection to the site of the pacemaker wire. Echocardiograms were negative for any vegetations. The patient responded to cefotaxime and trimethoprim-sulfamethoxazole therapy. We believe that this is the first case of H. parainfluenzae bacteremia associated with a pacemaker wire and localized by gallium scan.

  5. Bit-systolic arithmetic arrays using dynamic differential gallium arsenide circuits

    NASA Technical Reports Server (NTRS)

    Beagles, Grant; Winters, Kel; Eldin, A. G.

    1992-01-01

    A new family of gallium arsenide circuits for fine grained bit-systolic arithmetic arrays is introduced. This scheme combines features of two recent techniques of dynamic gallium arsenide FET logic and differential dynamic single-clock CMOS logic. The resulting circuits are fast and compact, with tightly constrained series FET propagation paths, low fanout, no dc power dissipation, and depletion FET implementation without level shifting diodes.

  6. Sequential technetium-99m/gallium-67 scintigraphic evaluation of subclinical osteomyelitis complicating fracture nonunion

    SciTech Connect

    Esterhai, J.; Alavi, A.; Mandell, G.A.; Brown, J.

    1985-01-01

    Twenty-four patients with a history of post-traumatic fracture nonunion underwent sequential /sup 99m/Tc and /sup 67/Ga citrate scintigraphy in an attempt to differentiate between posttraumatic fracture nonunion and nonunion complicated by subclinical osteomyelitis. Neither technetium nor gallium studies alone nor in combination, with or without clinical correlation, could help delineate between fracture nonunion and nonunion complicated by subclinical osteomyelitis because of the increased technetium and gallium radioisotope uptake associated with the nonunion site.

  7. Tumoral calcinosis associated with sarcoidosis and positive bone and gallium imaging

    SciTech Connect

    Wolpe, F.M.; Khedkar, N.Y.; Gordon, D.; Werner, P.; Shirazi, P.; Al-Sabban, M.H.

    1987-07-01

    A 63-year-old female with biopsy proven tumoral calcinosis presented with progressive and recurrent swelling and tenderness of the right hip, thigh, elbow, and wrist. Both gallium and bone imaging demonstrated intense, congruent uptake in these areas. This is the third case of tumoral calcinosis with sarcoidosis documented in the literature. However, these are the first published bone and gallium scans in a patient with a history of sarcoidosis and tumoral calcinosis.

  8. Study of liquid gallium at high pressure using synchrotron x-ray

    SciTech Connect

    Yu, Tony; Guo Quanzhong; Parise, John [Department of Geosciences, Mineral Physics Institute, Stony Brook University, Stony Brook, New York 11794-2100 (United States); Chen Jiuhua [Department of Geosciences, Mineral Physics Institute, Stony Brook University, Stony Brook, New York 11794-2100 (United States); Department of Mechanical and Materials Engineering, Center for the Study of Matters at Extreme Conditions, Florida International University, Miami, Florida 33199 (United States); Ehm, Lars [Department of Geosciences, Mineral Physics Institute, Stony Brook University, Stony Brook, New York 11794-2100 (United States); National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973-5000 (United States); Huang Shu [Department of Mechanical and Materials Engineering, Center for the Study of Matters at Extreme Conditions, Florida International University, Miami, Florida 33199 (United States); Luo Shengnian [Physics Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2012-06-01

    Liquid gallium has been studied at high pressure up to 2 GPa and ambient temperature in a diamond anvil cell using high energy synchrotron x-ray beam. The total x-ray scattering data of liquid gallium were collected up to Q = 12 A{sup -1} and analyzed using pair distribution functions (PDF). The results indicate that the first nearest neighbor peak and second nearest neighbor (shoulder) peak of PDF in liquid gallium does not change with pressure, whereas the higher order (i.e., third and fourth) nearest neighbor peaks shift towards shorter distance with increasing pressure. Reverse Monte Carlo modeling based on the observed data shows that the coordination number in the liquid gallium increases with pressure from 10.5 at 0.3 GPa to 11.6 at 2 GPa. An atomic arrangement similar to the crystalline phase of Ga(II) with coordination number of 12 is proposed for the locally dense-packed rigid unit in liquid gallium. The volume compression data derived from the structure modeling yield a bulk modulus of 12.1(6) GPa for liquid gallium.

  9. Fabrication and properties of gallium phosphide variable colour displays

    NASA Technical Reports Server (NTRS)

    Effer, D.; Macdonald, R. A.; Macgregor, G. M.; Webb, W. A.; Kennedy, D. I.

    1973-01-01

    The unique properties of single-junction gallium phosphide devices incorporating both red and green radiative recombination centers were investigated in application to the fabrication of monolithic 5 x 7 displays capable of displaying symbolic and alphanumeric information in a multicolor format. A number of potentially suitable material preparation techniques were evaluated in terms of both material properties and device performance. Optimum results were obtained for double liquid-phase-epitaxial process in which an open-tube dipping technique was used for n-layer growth and a sealed tipping procedure for subsequent p-layer growth. It was demonstrated that to prepare devices exhibiting a satisfactory range of dominant wavelengths which can be perceived as distinct emission colors extending from the red through green region of the visible spectrum involves a compromise between the material properties necessary for efficient red emission and those considered optimum for efficient green emission.

  10. Thermal lensing in silver gallium selenide parametric oscillator crystals.

    PubMed

    Marquardt, C L; Cooper, D G; Budni, P A; Knights, M G; Schepler, K L; Dedomenico, R; Catella, G C

    1994-05-20

    We performed an experimental investigation of thermal lensing in silver gallium selenide (AgGaSe(2)) optical parametric oscillator crystals pumped by a 2-µm laser at ambient temperature. We determined an empirical expression for the effective thermal focusing power in terms of the pump power, beam diameter, crystal length, and absorption coefficient. This relation may be used to estimate average power limitations in designing AgGaSe(2) optical parametric oscillators. We also demonstrated an 18% slope efficiency from a 2-µm pumped AgGaSe(2) optical parametric oscillator operated at 77 K, at which temperature thermal lensing is substantially reduced because of an increase in the thermal conductivity and a decrease in the thermal index gradient dn/dT. Cryogenic cooling may provide an additional option for scaling up the average power capability of a 2-µm pumped AgGaSe(2) optical parametric oscillator. PMID:20885687

  11. Design and Performance Estimates of an Ablative Gallium Electromagnetic Thruster

    NASA Technical Reports Server (NTRS)

    Thomas, Robert E.

    2012-01-01

    The present study details the high-power condensable propellant research being conducted at NASA Glenn Research Center. The gallium electromagnetic thruster is an ablative coaxial accelerator designed to operate at arc discharge currents in the range of 10-25 kA. The thruster is driven by a four-parallel line pulse forming network capable of producing a 250 microsec pulse with a 60 kA amplitude. A torsional-type thrust stand is used to measure the impulse of a coaxial GEM thruster. Tests are conducted in a vacuum chamber 1.5 m in diameter and 4.5 m long with a background pressure of 2 microtorr. Electromagnetic scaling calculations predict a thruster efficiency of 50% at a specific impulse of 2800 seconds.

  12. Transient Diffusion of Beryllium and Silicon in Gallium Arsenide

    NASA Astrophysics Data System (ADS)

    Haddara, Yaser M.; Bravman, John C.

    1998-08-01

    Transient diffusion is an increasingly important phenomenon as thermal budgets for real processes decrease and diffusion during sample growth becomes more important. To fully characterize dopant diffusion in gallium arsenide, an understanding must be developed of the dominant atomistic processes for a given dopant, as well as the sources of transient effects under a given set of experimental conditions. Theoretical, experimental, and simulation results were obtained to understand transient diffusivities of beryllium and silicon in grown-in and implanted samples. In implanted samples, by understanding implant damage and modeling the evolution of point defect populations, the observed transient effects can be explained. Such phenomena cannot account for the time-dependent diffusivity observed when the dopant is introduced during molecular beam epitaxial growth. Transient diffusivities for grown-in beryllium were investigated and explained by modeling the evolution of point defect populations as they increase beyond their equilibrium levels at the growth temperature to achieve equilibrium at the anneal temperature.

  13. Effect of irradiation temperature on dynamic recovery in gallium nitride

    NASA Astrophysics Data System (ADS)

    Jiang, W.; Weber, W. J.

    2006-01-01

    A single crystal gallium nitride film on sapphire was successively irradiated to a fluence of 4.5 Au3+/nm2 in different areas at varied temperatures ranging from 150 to 800 K. The temperature dependence of disorder on both the Ga and N sublattices has been investigated using a 3.736 MeV He+ backscattering analysis along the <0 0 0 1>- and < 1 0 1 bar 1 > -axial channeling directions. Significant dynamic recovery of disorder occurs over the applied temperature range. There is a higher degree of disorder on the N sublattice observed along the < 1 0 1 bar 1 > axis. Some of the defects produced during the irradiation in GaN are effectively shielded by the <0 0 0 1> axis.

  14. Dynamical and transport properties of liquid gallium at high pressures

    NASA Astrophysics Data System (ADS)

    Sheppard, D.; Mazevet, S.; Cherne, F. J.; Albers, R. C.; Kadau, K.; Germann, T. C.; Kress, J. D.; Collins, L. A.

    2015-06-01

    Quantum molecular dynamics (QMD) simulations are used to calculate the equation of state, structure, and transport properties of liquid gallium along the principal shock Hugoniot. The calculated Hugoniot is in very good agreement with experimental data up to a pressure of 150 GPa as well as with our earlier classical molecular dynamics calculations using a modified embedded atom method (MEAM) potential. The self-diffusion and viscosity calculated using QMD agree with experimental measurements better than the MEAM results, which we attribute to capturing the complexity of the electronic structure at elevated temperatures. Calculations of the DC conductivity were performed around the Hugoniot. Above a density of 7.5 g/cm3, the temperature increases rapidly along the Hugoniot, and the optical conductivity decreases, indicating simple liquid metal behavior.

  15. Coated gallium arsenide neutron detectors : results of characterizationmeasurements.

    SciTech Connect

    Klann, R. T.; Perret, G.; Sanders, J.

    2006-09-29

    Effective detection of special nuclear materials (SNM) is essential for reducing the threat associated with stolen or improvised nuclear devices. Passive radiation detection technologies are primarily based on gamma-ray detection and subsequent isotope identification or neutron detection (specific to neutron sources and SNM). One major effort supported by the Department of Homeland Security in the area of advanced passive detection is handheld or portable neutron detectors for search and localization tasks in emergency response and interdiction settings. A successful SNM search detector will not only be able to confirm the presence of fissionable materials but also establish the location of the source in as short of time as possible while trying to minimize false alarms due to varying background or naturally occurring radioactive materials (NORM). For instruments based on neutron detectors, this translates to detecting neutrons from spontaneous fission or alpha-n reactions and being able to determine the direction of the source (or localizing the source through subsequent measurements). Polyethylene-coated gallium arsenide detectors were studied because the detection scheme is based on measuring the signal in the gallium arsenide wafers from the electrical charge of the recoil protons produced from the scattering of neutrons from the hydrogen nucleus. The inherent reaction has a directional dependence because the neutron and hydrogen nucleus have equivalent masses. The assessment and measurement of polyethylene-coated gallium arsenide detector properties and characteristics was the first phase of a project being performed for the Department of Homeland Security and the results of these tests are reported in this report. The ultimate goal of the project was to develop a man-portable neutron detection system that has the ability to determine the direction of the source from the detector. The efficiency of GaAs detectors for different sizes of polyethylene layers and different angles between the detector and the neutron source were determined. Preliminary measurements with a neutron generator based on a deuterium-tritium reaction ({approx}14 MeV neutrons) were performed and the results are discussed. This report presents the results of these measurements in terms of efficiency and angular efficiency and compares them to Monte Carlo calculations to validate the calculation scheme in view of further applications. Based on the results of this study, the polyethylene-coated gallium arsenide detectors provide adequate angular resolution based on proton recoil detection from the neutron scattering reaction from hydrogen. However, the intrinsic efficiency for an individual detector is extremely low. Because of this low efficiency, large surface area detectors ( or a large total surface area from many small detectors) would be required to generate adequate statistics to perform directional detection in near-real time. Large surface areas could be created by stacking the detector wafers with only a negligible attenuation of source neutrons. However, the cost of creating such a large array of GaAs is cost-prohibitive at this time.

  16. Giant topological nontrivial band gaps in chloridized gallium bismuthide.

    PubMed

    Li, Linyang; Zhang, Xiaoming; Chen, Xin; Zhao, Mingwen

    2015-02-11

    Quantum spin Hall (QSH) effect is promising for achieving dissipationless transport devices but presently is achieved only at extremely low temperature. Searching for the large-gap QSH insulators with strong spin-orbit coupling (SOC) is the key to increase the operating temperature. We demonstrate theoretically that this can be solved in the chloridized gallium bismuthide (GaBiCl2) monolayer, which has nontrivial gaps of 0.95 eV at the ? point, and 0.65 eV for bulk, as well as gapless edge states in the nanoribbon structures. The nontrivial gaps due to the band inversion and SOC are robust against external strain. The realization of the GaBiCl2 monolayer will be beneficial for achieving QSH effect and related applications at high temperatures. PMID:25625786

  17. Mysterious absence of pair luminescence in gallium phosphide bismide

    NASA Astrophysics Data System (ADS)

    Christian, Theresa M.; Beaton, Daniel A.; Alberi, Kirstin; Fluegel, Brian; Mascarenhas, Angelo

    2015-06-01

    Gallium phosphide bismide (GaP1?xBix) epilayers with x up to 1.0% were grown via molecular beam epitaxy and their photoluminescence spectra were investigated at low temperatures. Surprisingly, the emission spectrum of the GaP1?xBix epilayers was fully described by isolated bismuth-bound exciton recombination at the A and B lines (2.232 and 2.229 eV, respectively) together with their phonon replicas, without a need for any description of recombination from bismuth pair or cluster states. These observations contrast with the typical behavior of energy transfer to lower-lying nitrogen pair states in GaP1?yNy at similar impurity concentrations and offer insights into the electronic structure evolution of GaP1?xBix.

  18. A high open-circuit voltage gallium nitride betavoltaic microbattery

    NASA Astrophysics Data System (ADS)

    Cheng, Zaijun; Chen, Xuyuan; San, Haisheng; Feng, Zhihong; Liu, Bo

    2012-07-01

    A high open-circuit voltage betavoltaic microbattery based on a gallium nitride (GaN) p-i-n homojunction is demonstrated. As a beta-absorbing layer, the low electron concentration of the n-type GaN layer is achieved by the process of Fe compensation doping. Under the irradiation of a planar solid 63Ni source with activity of 0.5 mCi, the open-circuit voltage of the fabricated microbattery with 2 × 2 mm2 area reaches as much as 1.64 V, which is the record value reported for betavoltaic batteries with 63Ni source, the short-circuit current was measured as 568 pA and the conversion effective of 0.98% was obtained. The experimental results suggest that GaN is a high-potential candidate for developing the betavoltaic microbattery.

  19. Thin-film gallium arsenide solar-cell research. Annual project report, March 1, 1980February 28, 1981

    Microsoft Academic Search

    1981-01-01

    The optimization of the deposition of gallium arsenide films of 10 ..mu..m thickness or less has been carried out with the objective of obtaining gallium arsenide films with uniform microstructure and good electrical properties. Gallium arsenide films of 10 ..mu..m or less thickness deposited on tungsten\\/graphite substrates exhibit, in most cases, pronounced shunting effects in large area MOS solar cells

  20. Interaction of Gallium Nitrate with Fludarabine and Iron Chelators: Effects on the Proliferation of Human Leukemic HL60 Cells

    Microsoft Academic Search

    Joel H. Lundberg; Christopher R. Chitambar

    Earlier studies have shown that transferrin-gallium inhibits cellular iron incorporation and blocks DNA synthesis by decreasing the activity of the iron-dependent M2 subunit of ribonucleotide reducíase. We ex amined the growth-inhibitory effects of gallium nitrate in combination with clinically relevant inhibitors of ribonucleotide reducíase fludarabine (an Ml subunit inhibitor), and iron chelators (M2 subunit inhibitors). Fludarabine and gallium nitrate in

  1. Solar neutrino measurement with radiochemical gallium detector (GALLEX)

    NASA Astrophysics Data System (ADS)

    von Ammon, Reinhard

    1994-04-01

    The GALLEX experiment for the detection of solar neutrinos by means of a radiochemical gallium detector is operated by groups from Italy, France, Germany, Israel and the USA in the Gran Sasso underground laboratory (LNGS) near L'Aquila (Italy). It consists of (1) the technical scale tank made of glass fiber reinforced polyester fabric containing 101 metric tons (54 cu m) of a highly concentrated (8 moles per liter) GaCl3 solution; (2) a gas sparging system for desorption of GeCl4 which has been formed by interaction of the neutrinos with gallium according to Ga-71 + nue yields Ge-71 + e(-) and by addition of ca. 1 mg of a stable Ge isotope; (3) the absorption columns for concentration of GeCl4 into a volume of 1 l of water; (4) the laboratory scale apparatus for conversion of GeCl4 to GeH4 and mixing with the counting gas Xe; (5) the counter filling station, and (6) the low level proportional counters. Contributions of possible side reactions which have to be corrected for, e.g. by cosmic muons, fast neutrons and alpha-emitters are discussed, as well as the purification of the target solution from long-lived ( t1/2 = 271 d) cosmogenic Ge-68. A first preliminary result after one year of solar neutrino measurement is presented. This constitutes the first direct measurement of the basic proton-proton fusion reaction in the core of the sun. This result, appreciably below the predictions of the standard solar model (SSM) (132 Solar Neutrino Units (SNU)) can be interpreted, together with the results of the chlori ne and KAMIOKANDE experiments either by astrophysics or by neutrino oscillations (Mikheyev-Smirnov-Wolfenstein (MSW) effect). The solar neutrino measurements are continuing and a calibration experiment with a Cr-51 source is in preparation.

  2. Study of Magnetohydrodynamic Surface Waves on Liquid Gallium

    SciTech Connect

    Hantao Ji; William Fox; David Pace; H.L. Rappaport

    2004-05-13

    Magnetohydrodynamic (MHD) surface waves on liquid gallium are studied theoretically and experimentally in the small magnetic Reynolds number limit. A linear dispersion relation is derived when a horizontal magnetic field and a horizontal electric current is imposed. No wave damping is found in the shallow liquid limit while waves always damp in the deep liquid limit with a magnetic field parallel to the propagation direction. When the magnetic field is weak, waves are weakly damped and the real part of the dispersion is unaffected, while in the opposite limit waves are strongly damped with shortened wavelengths. In a table-top experiment, planar MHD surface waves on liquid gallium are studied in detail in the regime of weak magnetic field and deep liquid. A non-invasive diagnostic accurately measures surface waves at multiple locations by reflecting an array of lasers off the surface onto a screen, which is recorded by an Intensified-CCD camera. The measured dispersion relation is consistent with the linear theory with a reduced surface tension likely due to surface oxidation. In excellent agreement with linear theory, it is observed that surface waves are damped only when a horizontal magnetic field is imposed parallel to the propagation direction. No damping is observed under a perpendicular magnetic field. The existence of strong wave damping even without magnetic field suggests the importance of the surface oxide layer. Implications to the liquid metal wall concept in fusion reactors, especially on the wave damping and a Rayleigh-Taylor instability when the Lorentz force is used to support liquid metal layer against gravity, are discussed.

  3. Saddle-like deformation in a dielectric elastomer actuator embedded with liquid-phase gallium-indium electrodes

    SciTech Connect

    Wissman, J., E-mail: jwissman@andrew.cmu.edu [Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Finkenauer, L. [Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Deseri, L. [DICAM, Department of Mechanical, Civil and Environmental Engineering, University of Trento, via Mesiano 77 38123 Trento (Italy); TMHRI-Department of Nanomedicine, The Methodist Hospital Research Institute, 6565 Fannin St., MS B-490 Houston, Texas 77030 (United States); Mechanics, Materials and Computing Center, CEE and ME-CIT, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Majidi, C. [Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Robotics Institute and Department of Civil and Environmental Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States)

    2014-10-14

    We introduce a dielectric elastomer actuator (DEA) composed of liquid-phase Gallium-Indium (GaIn) alloy electrodes embedded between layers of poly(dimethylsiloxane) (PDMS) and examine its mechanics using a specialized elastic shell theory. Residual stresses in the dielectric and sealing layers of PDMS cause the DEA to deform into a saddle-like geometry (Gaussian curvature K<0). Applying voltage ? to the liquid metal electrodes induces electrostatic pressure (Maxwell stress) on the dielectric and relieves some of the residual stress. This reduces the longitudinal bending curvature and corresponding angle of deflection ?. Treating the elastomer as an incompressible, isotropic, NeoHookean solid, we develop a theory based on the principle of minimum potential energy to predict the principal curvatures as a function of ?. Based on this theory, we predict a dependency of ? on ? that is in strong agreement with experimental measurements performed on a GaIn-PDMS composite. By accurately modeling electromechanical coupling in a soft-matter DEA, this theory can inform improvements in design and fabrication.

  4. Measurement of solar proton-proton fusion neutrinos with a Soviet-American gallium experiment: Technical progress report

    SciTech Connect

    Cherry, M.L.

    1989-06-01

    A gallium solar neutrino detector is sensitive to low-energy proton-proton fusion neutrinos. A flux of 70 SNU is expected in a gallium detector from the p-p reaction independent of solar model calculations. If, however, neutrino oscillations in the solar interior are responsible for the suppressed /sup 8/B flux measured by the Homestake /sup 37/Cl experiment, then a comparison of the gallium and chlorine results may make possible a determination of the neutrino mass difference and mixing angle. A 60-ton gallium detector is currently being constructed in the Baksan Laboratory in the Soviet Union, and should be taking data by the end of 1989.

  5. Measurement of solar proton-proton fusion neutrinos with a Soviet-American gallium experiment: Technical progress report

    SciTech Connect

    Cherry, M.L.

    1988-11-01

    A gallium solar neutrino detector is sensitive to low-energy proton-proton fusion neutrinos. A flux of 70 SNU is expected in a gallium detector from the p-p reaction independent of solar model calculations. If, however, neutrino oscillations in the solar interior are responsible for the suppressed /sup 8/B flux measured by the Homestake /sup 37/Cl experiment, then a comparison of the gallium and chlorine results may make possible a determination of the neutrino mass difference and mixing angle. A 60-ton gallium detector is currently being constructed in the Baksan laboratory in the Soviet Union, and should be taking data by early 1989.

  6. Metal alloy identifier

    DOEpatents

    Riley, William D. (Avondale, MD); Brown, Jr., Robert D. (Avondale, MD)

    1987-01-01

    To identify the composition of a metal alloy, sparks generated from the alloy are optically observed and spectrographically analyzed. The spectrographic data, in the form of a full-spectrum plot of intensity versus wavelength, provide the "signature" of the metal alloy. This signature can be compared with similar plots for alloys of known composition to establish the unknown composition by a positive match with a known alloy. An alternative method is to form intensity ratios for pairs of predetermined wavelengths within the observed spectrum and to then compare the values of such ratios with similar values for known alloy compositions, thereby to positively identify the unknown alloy composition.

  7. Synthesis and characterization of electrodeposited copper indium selenide and copper (indium, gallium) selenide thin films

    NASA Astrophysics Data System (ADS)

    Friedfeld, Robert Bonheur

    Electrodeposition is a cost effective method for growing polycrystalline thin films which is not limited by substrate/superstrate size and does not require the use of a vacuum. In this research, CuInSe2 and Cu(In,Ga)Se 2 polycrystalline thin films have been synthesized by electrodeposition. Both of these materials have very high absorption coefficients when compared to Si and GaAs, and can have their band gaps adjusted through the control of their stoichiometries. Both CuInSe2 and Cu(In,Ga)Se2 are direct band gap semiconductors with the chalcopyrite crystal structure. Therefore, these materials are important for use in high efficiency photovoltaic solar cells. In an attempt to understand how the composition, morphology and crystallinity depend on electrodeposition conditions, various thin films of CuInSe2 and Cu(In,Ga)Se2 were grown by electrodeposition. These films were then characterized by a number of characterization techniques which include (1) scanning electron microscopy, (2) scanning tunneling microscopy, (3) energy dispersive spectroscopy, (4) X-ray diffraction, and (5) Auger electron spectroscopy. Results based on this research indicate two main conclusions. (1) Modulated or layered films of CuInSe2 can be grown by electrodeposition. Measurements made by Scanning Tunneling Microscopy of cleaved cross sections of the CuInSe2 layered films indicate the successful formation of layers. (2) Cu(In,Ga)Se2 thin films can be electrodeposited by a two-step process with minimal post treatment steps. The process developed here can be done at room temperature. Two electrochemical baths are used, one to electrodeposit a CuGa2 binary alloy, followed by the electrodeposition of a CuInSe2 thin film from another bath. The resulting bilayer film is then annealed in flowing argon at an elevated temperature to form the CIGS compound. Characterization results from measurements made by X-ray diffraction show that the resulting films maintain the basic chalcopyrite structure while the Bragg peaks shift to larger diffraction angles with increasing gallium content in the film. This is evidence to support the successful formation of CIGS films. This data is further corroborated by the energy dispersive spectroscopy and Auger electron spectroscopy data.

  8. Cleansing the colon in gallium-67 scintigraphy: a prospective comparison of regimens

    SciTech Connect

    Novetsky, G.J.; Turner, D.A.; Ali, A.; Raynor, W.J. Jr.; Fordham, E.W.

    1981-01-01

    Colonic accumulation of gallium-67 frequently complicates the interpretation of gallium-67 scintigrams. Although various modes of cleansing the colon prior to scintigraphy have been suggested, there is controversy over their efficacy and none have been tested prospectively. Three hundred nine patients undergoing gallium-67 scintigraphy were randomly assigned to one of four cleansing regimens: (1) a high fiber diet (78 patients); (2) castor oil (76); (3) milk of magnesia and cascara (76); and (4) not preparation (79). Patient compliance rates for the four regimens were 17%, 32%, 36%, and 46%, respectively. After noncompliant patients were excluded, gallium-67 scintigrams were graded for colonic activity on a scale of 0-3 by three independent, experienced observers. Gallium-67 activity in the colon was significantly less after administration of castor oil than after no preparation (p . 0.047). A high fiber diet also resulted in a substantial reduction of colonic activity when compared with no preparation; the difference, however, was not statistically significant (p . 0.083). Regimen 3 did not produce significantly better results than regimen 4 (p . 0.42). A major impediment to the success of any cleansing regimen seems to be poor compliance of patients.

  9. Cleansing the colon in gallium-67 scintigraphy: a prospective comparison of regimens

    SciTech Connect

    Novetsky, G.J.; Turner, D.A.; Ali, A.; Raynor, W.J.; Fordham, E.W.

    1981-11-01

    Colonic accumulation of gallium-67 frequently complicates the interpretation of gallium-67 scintigrams. Although various modes of cleansing the colon prior to scintigraphy have been suggested, there is controversy over their efficacy and none have been tested prospectively. Three hundred nine patients undergoing gallium-67 scintigraphy were randomly assigned to one of four cleansing regimens: (1) a high fiber diet (78 patients); (2) castor oil (76); (3) milk of magnesia and cascara (76); and (4) no preparation (79). Patient compliance rates for the four regimens were 17%, 32%, 36%, and 46%, respectively. After noncompliant patients were excluded, gallium-67 scintigrams were graded for colonic activity on a scale of 0-3 by three independent, experienced observers. Gallium-67 activity in the colon was significantly less after adminstration of castor oil than after no prepartion (p = 0.083). Regimen 3 did not produce significantly better results than regimen 4 (p = 0.42). A major impediment to the success of any cleansing regimen seems to be poor compliance of patients.

  10. Selective etching of focused gallium ion beam implanted regions from silicon as a nanofabrication method

    NASA Astrophysics Data System (ADS)

    Han, Zhongmei; Vehkamäki, Marko; Mattinen, Miika; Salmi, Emma; Mizohata, Kenichiro; Leskelä, Markku; Ritala, Mikko

    2015-07-01

    A focused ion beam (FIB) is otherwise an efficient tool for nanofabrication of silicon structures but it suffers from the poor thermal stability of the milled surfaces caused by segregation of implanted gallium leading to severe surface roughening upon already slight annealing. In this paper we show that selective etching with KOH:H2O2 solutions removes the surface layer with high gallium concentration while blocking etching of the surrounding silicon and silicon below the implanted region. This remedies many of the issues associated with gallium FIB nanofabrication of silicon. After the gallium removal sub-nm surface roughness is retained even during annealing. As the etching step is self-limited to a depth of 25–30 nm for 30 keV ions, it is well suited for defining nanoscale features. In what is essentially a reversal of gallium resistless lithography, local implanted areas can be prepared and then subsequently etched away. Nanopore arrays and sub-100 nm trenches can be prepared this way. When protective oxide masks such as Al2O3 grown with atomic layer deposition are used together with FIB milling and KOH:H2O2 etching, ion-induced amorphization can be confined to sidewalls of milled trenches.

  11. Selective etching of focused gallium ion beam implanted regions from silicon as a nanofabrication method.

    PubMed

    Han, Zhongmei; Vehkamäki, Marko; Mattinen, Miika; Salmi, Emma; Mizohata, Kenichiro; Leskelä, Markku; Ritala, Mikko

    2015-07-01

    A focused ion beam (FIB) is otherwise an efficient tool for nanofabrication of silicon structures but it suffers from the poor thermal stability of the milled surfaces caused by segregation of implanted gallium leading to severe surface roughening upon already slight annealing. In this paper we show that selective etching with KOH:H2O2 solutions removes the surface layer with high gallium concentration while blocking etching of the surrounding silicon and silicon below the implanted region. This remedies many of the issues associated with gallium FIB nanofabrication of silicon. After the gallium removal sub-nm surface roughness is retained even during annealing. As the etching step is self-limited to a depth of 25-30 nm for 30 keV ions, it is well suited for defining nanoscale features. In what is essentially a reversal of gallium resistless lithography, local implanted areas can be prepared and then subsequently etched away. Nanopore arrays and sub-100 nm trenches can be prepared this way. When protective oxide masks such as Al2O3 grown with atomic layer deposition are used together with FIB milling and KOH:H2O2 etching, ion-induced amorphization can be confined to sidewalls of milled trenches. PMID:26062985

  12. Gallium-mediated siderophore quenching as an evolutionarily robust antibacterial treatment

    PubMed Central

    Ross-Gillespie, Adin; Weigert, Michael; Brown, Sam P.; Kümmerli, Rolf

    2014-01-01

    Background and objectives: Conventional antibiotics select strongly for resistance and are consequently losing efficacy worldwide. Extracellular quenching of shared virulence factors could represent a more promising strategy because (i) it reduces the available routes to resistance (as extracellular action precludes any mutations blocking a drug’s entry into cells or hastening its exit) and (ii) it weakens selection for resistance, as fitness benefits to emergent mutants are diluted across all cells in a cooperative collective. Here, we tested this hypothesis empirically. Methodology: We used gallium to quench the iron-scavenging siderophores secreted and shared among pathogenic Pseudomonas aeruginosa bacteria, and quantitatively monitored its effects on growth in vitro. We assayed virulence in acute infections of caterpillar hosts (Galleria mellonella), and tracked resistance emergence over time using experimental evolution. Results: Gallium strongly inhibited bacterial growth in vitro, primarily via its siderophore quenching activity. Moreover, bacterial siderophore production peaked at intermediate gallium concentrations, indicating additional metabolic costs in this range. In vivo, gallium attenuated virulence and growth—even more so than in infections with siderophore-deficient strains. Crucially, while resistance soon evolved against conventional antibiotic treatments, gallium treatments retained their efficacy over time. Conclusions: Extracellular quenching of bacterial public goods could offer an effective and evolutionarily robust control strategy. PMID:24480613

  13. Synthesis and Structural characterization of ?-ketoiminate-stabilized gallium hydrides for chemical vapor deposition applications.

    PubMed

    Marchand, Peter; Pugh, David; Parkin, Ivan P; Carmalt, Claire J

    2014-08-11

    Bis-?-ketoimine ligands of the form [(CH2 )n {N(H)C(Me)?CHC(Me)?O}2 ] (L(n) H2 , n=2, 3 and 4) were employed in the formation of a range of gallium complexes [Ga(L(n) )X] (X=Cl, Me, H), which were characterised by NMR spectroscopy, mass spectrometry and single-crystal X-ray diffraction analysis. The ?-ketoimine ligands have also been used for the stabilisation of rare gallium hydride species [Ga(L(n) )H] (n=2 (7); n=3 (8)), which have been structurally characterised for the first time, confirming the formation of five-coordinate, monomeric species. The stability of these hydrides has been probed through thermal analysis, revealing stability at temperatures in excess of 200?°C. The efficacy of all the gallium ?-ketoiminate complexes as molecular precursors for the deposition of gallium oxide thin films by chemical vapour deposition (CVD) has been investigated through thermogravimetric analysis and deposition studies, with the best results being found for a bimetallic gallium methyl complex [L(3) {GaMe2 }2 ] (5) and the hydride [Ga(L(3) )H] (8). The resulting films (F5 and F8, respectively) were amorphous as-deposited and thus were characterised primarily by XPS, EDXA and SEM techniques, which showed the formation of stoichiometric (F5) and oxygen-deficient (F8) Ga2 O3 thin films. PMID:25043194

  14. Thin film gallium arsenide solar cell research. Third quarterly project report, September 1, 1980November 30, 1980. [Antireflection coating

    Microsoft Academic Search

    1980-01-01

    The major objective of this contract is to produce gallium arsenide solar cells of 10% conversion efficiency in films of less than 10 micrometers thick which have been deposited by chemical vapor deposition on graphite or tungsten coated graphite substrates. Major efforts during this quarter were directed to: (1) the optimization of the deposition of gallium arsenide films of 10

  15. Gallium-arsenide deep-level tunnel diode with record negative conductance and record peak current density

    E-print Network

    Woodall, Jerry M.

    deep-levels in low-temperature-grown (LTG) gallium-arsenide (GaAs) are demonstrated. These tunnel resistance devices; Semiconductor defects; Semiconductor diodes; Semiconductor impurities; Tunnel diodes 1-temperature-grown (LTG) gallium-arsenide (GaAs) gave rise to tunnel diodes having very negative conductance and large

  16. Synthesis and microstructure of gallium phosphide nanowires W. S. Shi, Y. F. Zheng, N. Wang,a)

    E-print Network

    Zheng, Yufeng

    of various nanotubes, nanowires, and composite nanostructures has stimulated an intense in- terestSynthesis and microstructure of gallium phosphide nanowires W. S. Shi, Y. F. Zheng, N. Wang,a) C. S May 2001 Gallium phosphide GaP nanowires of 22 nm in diameter and hundreds micrometers in length were

  17. Micro and nano-structured green gallium indium nitride/gallium nitride light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Stark, Christoph J. M.

    Light-emitting diodes (LEDs) are commonly designed and studied based on bulk material properties. In this thesis different approaches based on patterns in the nano and micrometer length scale range are used to tackle low efficiency in the green spectral region, which is known as “green gap”. Since light generation and extraction are governed by microscopic processes, it is instructive to study LEDs with lateral mesa sizes scaled to the nanometer range. Besides the well-known case of the quantum size effect along the growth direction, a continuous lateral scaling could reveal the mechanisms behind the purported absence of a green gap in nanowire LEDs and the role of their extraction enhancement. Furthermore the possibility to modulate strain and piezoelectric polarization by post growth patterning is of practical interest, because the internal electric fields in conventional wurtzite GaN LEDs cause performance problems. A possible alternative is cubic phase GaN, which is free of built-in polarization fields. LEDs on cubic GaN could show the link between strong polarization fields and efficiency roll-off at high current densities, also known as droop. An additional problem for all nitride-based LEDs is efficient light extraction. For a planar GaN LED only roughly 8% of the generated light can be extracted. Novel lightextraction structures with extraction-favoring geometry can yield significant increase in light output power. To investigate the effect of scaling the mesa dimension, micro and nano-sized LED arrays of variable structure size were fabricated. The nano-LEDs were patterned by electron beam lithography and dry etching. They contained up to 100 parallel nano-stripe LEDs connected to one common contact area. The mesa width was varied over 1 ?m, 200 nm, and 50 nm. These LEDs were characterized electrically and optically, and the peak emission wavelength was found to depend on the lateral structure size. An electroluminescence (EL) wavelength shift of 3 nm towards smaller values was observed when the stripe width was reduced from 1 ?m to 50 nm. At the same time a strong fourfold enhancement of the light emission from the patterned region over the unpatterned area was observed. Micro-patterned LEDs showed non-linear scaling of the light output power, and an enhancement of 39 % was achieved for structures with an area fill ratio of 0.5 over an LED with square mesa. Growth of cubic GaN and cubic GaInN/GaN LEDs was shown by M-OVPE in Vshaped grooves formed by the {111} planes of etched silicon. SEM images of the GaN layer in small ( 0.5 ?m) regions show a contrast change where the phase boundary between cubic and wurtzite GaN is expected to occur. The growth parameter space is explored for optimal conditions while minimizing the alloying problem for GaN growth on Si. The cubic GaN phase is confirmed by electron back-scatter diffraction (EBSD) in the V-groove center, whereas wurtzite GaN is found near the groove edges. Luminescence of undoped GaN and GaInN/GaN multi-quantum well structures was studied by cathodoluminescence (CL). The undoped cubic GaN structure showed strong band-edge luminescence at 385 nm (3.22 eV) at 78 K, whereas for the MQW device strong emission at 498 nm is observed, even at room temperature. Full cubic LED structures were grown, and wavelength-stable electroluminescence at 489 nm was demonstrated. LEDs with integrated light extraction structures are grown on free-standing GaN substrates with different off-cut angles. The devices with different off-cut show pronounced features at the top surface that also penetrate the active region. For a 2.24° off-cut, these features resemble fish scales, where the feature sizes are in the ?m-range. The 2.24° off-cut LED shows a 3.6-fold increased light output power compared to a LED on virtually on-axis substrate with 0.06° off-cut. The enhancement found in the fish scale LEDs is attributed to increased light scattering, effectively reducing the fraction of trapped light. These results show the potential of structures on the micro and nanometer scale

  18. QUANTIFICATION OF GALLIUM IN DRIED RESIDUE SAMPLES BY XRF: AN IMPROVED SAMPLE PREPARATION METHOD FOR ANALYZING PLUTONIUM METAL.

    SciTech Connect

    Worley, C. G. (Christopher G.)

    2001-01-01

    A novel XRF sample preparation method was investigated to quantify the concentration of gallium in plutonium metal and minimize the possibility of contaminating the instrument with radioactive material. To prepare homogenous specimens and to add an internal standard, the plutonium must first be dissolved. The currently established method then entails removing the plutonium by chromatography and analyzing the gallium remaining in solution. In the work presented here, plutonium solution aliquots containing zinc as an internal standard were cast onto Mylar, dried, and analyzed by XRF. Aqueous standards containing gallium and zinc were first cast as dried residues, and these residue standards were analyzed and calibrated. More recently aqueous standards containing plutonium, gallium, and zinc were prepared, cast as dried spots, and calibrated. Very linear calibrations were obtained for both sets of standards when zinc was used as the internal standard (RMS values =1% of the standards concentration range). Hence, this dried residue process appears very promising for quantifying gallium in plutonium metal.

  19. Defect levels in indium and gallium doped zinc selenide

    NASA Astrophysics Data System (ADS)

    Qidwai, A. A.; Woods, J.

    1982-09-01

    Indium and gallium dopants in ZnSe display unusual properties in that although they act as shallow donors in low concentration, complex compensation effects appear to occur at high concentration, so that the resistivity increases with increasing impurity content. In order to investigate these effects, the techniques of transient photocapacitance and transient photocurrent have been used to study the incidence of deep levels in Schottky diodes formed on ZnSe: In and ZnSe: Ga. Shallow levels have also been investigated using the photocapacitance method advocated by Marfaing. In indium doped crystals, acceptor levels were found at 0.59 and 0.41 eV above the valence band. The acceptor at 0.59 eV is identified as the zinc vacancy-substitutional indium complex part of the self-activated luminescence centre. The 0.41 eV acceptor became more apparent as the indium content was increased and presumably contributes to the observed donor compensation effects. For comparison diodes fabricated on copper doped ZnSe were examined and found to exhibit an acceptor level at 0.67 eV.

  20. Soft tissue reactions evoked by implanted gallium phosphide.

    PubMed

    Linsmeier, Cecilia E; Wallman, Lars; Faxius, Linda; Schouenborg, Jens; Bjursten, Lars M; Danielsen, Nils

    2008-12-01

    Neural devices may play an important role in the diagnosis and therapy of several clinical conditions, such as stroke, trauma or neurodegenerative disorders, by facilitating motor and pain control. Such interfaces, chronically implanted in the CNS, need to be biocompatible and have the ability to stimulate and record nerve signals. However, neural devices of today are not fully optimized. Nanostructured surfaces may improve electrical properties and lower evoked tissue responses. Vertical gallium phosphide (GaP) nanowires epitaxially grown from a GaP surface is one way of creating nanostructured electrodes. Thus, we chose to study the soft tissue reactions evoked by GaP surfaces. GaP and the control material titanium (Ti) were implanted in the rat abdominal wall for evaluation of tissue reactions after 1, 6, or 12 weeks. The foreign-body response was evaluated by measuring the reactive capsule thickness and by quantification of ED1-positive macrophages and total cells in the capsule. Furthermore, the concentration of Ga was measured in blood, brain, liver and kidneys. Statistically significant differences were noticed between GaP and Ti at 12 weeks for total and ED1-positive cell densities in the capsule. The chemical analysis showed that the concentration of Ga in brain, liver and kidneys increased during 12 weeks of implantation, indicating loss of Ga from the implant. Taken together, our results show that the biocompatible properties of GaP are worse than those of the well-documented biomaterial Ti. PMID:18801568

  1. Novel uncooled detector based on gallium nitride micromechanical resonators

    NASA Astrophysics Data System (ADS)

    Gokhale, Vikrant J.; Sui, Yu; Rais-Zadeh, Mina

    2012-06-01

    This work presents measured results demonstrating an uncooled infrared (IR) detector based on gallium nitride (GaN) micromechanical resonators. GaN-based photonic detectors are typically designed to operate in the ultraviolet (UV) regime as the absorption spectrum of wide-band gap GaN peaks at a wavelength of ~360 nm. In contrast, the transduction mechanism of the device presented in this work is the pyroelectric perturbation of a GaN micromechanical resonator, allowing the detection of radiation in the IR regime. IR radiation within the absorption spectrum of the resonating stack material (mainly the IR absorber) is converted into heat causing pyroelectric charge release, which in turn shifts the resonant frequency via changes in the acoustic velocity of GaN. A thin-film IR absorber based on carbon-nanotube nanocomposite is proposed, which offers IR absorptivity of more than 95%. As a proof of concept, we demonstrate a GaN resonant detector operated at 119 MHz, which exhibits an IR sensitivity of ~4 Hz/10nW.

  2. Investigation of a Gallium MPD Thruster with an Ablating Cathode

    NASA Technical Reports Server (NTRS)

    Thomas, Robert E.; Burton, Rodney L.; Polzin, Kurt A.

    2010-01-01

    Arc impedance, exhaust velocity, and plasma probe measurements are presented. The thruster is driven by a 50 microsecond pulse from a 6.2 milliohm pulse forming network, and gallium is supplied to the discharge by evaporation of the cathode. The arc voltage is found to vary linearly with the discharge current with an arc impedance of 6.5 milliohms. Electrostatic probes yield an exhaust velocity that is invariant with the discharge current and has a peak value of 20 kilometers per second, which is in reasonable agreement with the value (16 plus or minus 1 kilometer per second) calculated from the mass bit and discharge current data. Triple probe measurements yield on axis electron temperatures in the range of 0.8-3.8 eV, electron densities in the range of 1.6 x 10(exp 21) to 2.1 x 10(exp 22) per cubic meter, and a divergence half angle of 16 degrees. Measurements within the interelectrode region yield a peak magnetic field of 0.8 T, and the observed radial trends are consistent with an azimuthally symmetric current distribution. A cathode power balance model is coupled with an ablative heat conduction model predicting mass bit values that are within 20% of the experimental values.

  3. Gallium Nitride high temperature electronics for Venus 90-day Lander

    NASA Astrophysics Data System (ADS)

    Frampton, Robert; Peltz, Leora; Rubin, Seymour

    2008-09-01

    NASA Science exploration Roadmap includes a "Venus Mobile Lander" mission to operate on the surface of Venus for at least 90 days. Venus Mobile Lander will explore Venus surface as either an aerial vehicle or rover for several months. Previous missions to Venus operated for less than 2 hours. Electronics available today is not capable of supporting design of spacecraft avionics, power systems, or science instruments to operate in the Venus surface environment for 90 days. Thus this long duration mission will spawn a technology development program that can support science instrument and spacecraft design to meet mission requirements. Boeing, together with HRL Laboratory, is developing high temperature electronics for the Venus environment (480 Celsius, 90 bars carbon dioxide atmosphere) using the gallium nitride technology. Examples from our recent validation tests in harsh environments illustrate the performance of the electronic components and modules. In addition to the GaN-based semiconductor material, the characteristics, reliability and viability of the electronics is affected by constituent materials (metallization, dielectric layers) and by the packaging (die attach, wire bonding).

  4. A molecular dynamics investigation of low temperature gallium arsenide

    NASA Astrophysics Data System (ADS)

    Landman, Joseph Irwin

    An theoretical investigation of point defect and defect complexes in low temperature Gallium Arsenide (LT GaAs) has been undertaken, specifically targeting the question of the location of excess Arsenic storage in this non-stoichiometric bulk material. Molecular dynamics techniques has been used to form low energy defect configurations for study, specifically those defects which allow for an excess of Arsenic. The results of these calculations indicate that various split interstitial and split antisite defect configurations may be able to explain measurements that indicate a defect donor band between 0.5 to 0.3 eV below the conduction band edge in the LT GaAs material. Moreover, a calculation of relative defect abundances for split interstitials and split antisites indicates that the split antisite complex can account for extra As in the lattice that is not visible to EPR or absorption measurements as an antisite. Additionally, the split antisite, split interstitial, and a nearest neighbor defect complex may be able to explain the observed temperature dependent defect concentrations.

  5. LASERS: Efficient neodymium-doped gadolinium gallium garnet crystal laser

    NASA Astrophysics Data System (ADS)

    Doroshenko, Maxim E.; Osiko, Vyacheslav V.; Sigachev, V. B.; Timoshechkin, M. I.

    1991-07-01

    An investigation was made of the stimulated emission parameters of a laser utilizing a gadolinium gallium garnet crystal doped with neodymium ions (YAG:Nd) at the 1.062 ?m wavelength. The free-running efficiency was the highest so far achieved for flashlamp-pumped lasers utilizing unsensitized garnets. For an active element 8 mm in diameter and 120 mm long the absolute efficiency was 5.4% and the differential efficiency was 5.9%. The average free-running power was 170 W. A comparison was made of the optical powers of thermal lenses in cylindrical GGG:Nd and YAG:Nd active elements and this was found to be 2.4 times higher for a GGG:Nd crystal at the same pump powers. It was shown that by using traditional methods of compensating for the thermal lens in cylindrical active elements, it is possible to develop pulsed GGG:Nd crystal lasers having an average output power higher than 100 W, an efficiency of ~ 4%, and an angular divergence of less than 10 mrad.

  6. Deprotecting Thioacetyl-Terminated Terphenyldithiol for Assembly on Gallium Arsenide

    SciTech Connect

    Krapchetov,D.; Ma, H.; Jen, A.; Fischer, D.; Loo, Y.

    2008-01-01

    We characterize the assembly of terphenyldithiol (TPDT) on gallium arsenide (GaAs) from ethanol (EtOH) and tetrahydrofuran (THF) as a function of ammonium hydroxide (NH4OH) concentration. NH4OH facilitates the conversion of thioacetyl end groups of the TPDT precursor to thiolates in the assembly solution. The final structure of TPDT assembled on GaAs is sensitive not only to the assembly solvent but also to NH4OH concentration. In the presence of low concentrations of NH4OH (1 mM), TPDT assemblies from EtOH are oriented upright. The same assemblies are less upright when adsorption is carried out at higher NH4OH concentrations. In THF, TPDT does not adsorb significantly on GaAs at low NH4OH concentrations. The surface coverage and structural organization of these assemblies improve with increasing NH4OH concentrations, although these assemblies are never as organized as those from EtOH. The difference in the final structure of TPDT assemblies is attributed to differences in the thiolate fraction in the assembly solution at the point of substrate immersion.

  7. Deprotecting thioacetyl-terminated terphenyldithiol for assembly on gallium arsenide.

    PubMed

    Krapchetov, Dmitry A; Ma, Hong; Jen, Alex K Y; Fischer, Daniel A; Loo, Yueh-Lin

    2008-02-01

    We characterize the assembly of terphenyldithiol (TPDT) on gallium arsenide (GaAs) from ethanol (EtOH) and tetrahydrofuran (THF) as a function of ammonium hydroxide (NH4OH) concentration. NH4OH facilitates the conversion of thioacetyl end groups of the TPDT precursor to thiolates in the assembly solution. The final structure of TPDT assembled on GaAs is sensitive not only to the assembly solvent but also to NH4OH concentration. In the presence of low concentrations of NH4OH (1 mM), TPDT assemblies from EtOH are oriented upright. The same assemblies are less upright when adsorption is carried out at higher NH4OH concentrations. In THF, TPDT does not adsorb significantly on GaAs at low NH4OH concentrations. The surface coverage and structural organization of these assemblies improve with increasing NH4OH concentrations, although these assemblies are never as organized as those from EtOH. The difference in the final structure of TPDT assemblies is attributed to differences in the thiolate fraction in the assembly solution at the point of substrate immersion. PMID:18163654

  8. Gallium arsenide (GaAs) quantum photonic waveguide circuits

    NASA Astrophysics Data System (ADS)

    Wang, Jianwei; Santamato, Alberto; Jiang, Pisu; Bonneau, Damien; Engin, Erman; Silverstone, Joshua W.; Lermer, Matthias; Beetz, Johannes; Kamp, Martin; Höfling, Sven; Tanner, Michael G.; Natarajan, Chandra M.; Hadfield, Robert H.; Dorenbos, Sander N.; Zwiller, Val; O'Brien, Jeremy L.; Thompson, Mark G.

    2014-09-01

    Integrated quantum photonics is a promising approach for future practical and large-scale quantum information processing technologies, with the prospect of on-chip generation, manipulation and measurement of complex quantum states of light. The gallium arsenide (GaAs) material system is a promising technology platform, and has already successfully demonstrated key components including waveguide integrated single-photon sources and integrated single-photon detectors. However, quantum circuits capable of manipulating quantum states of light have so far not been investigated in this material system. Here, we report GaAs photonic circuits for the manipulation of single-photon and two-photon states. Two-photon quantum interference with a visibility of 94.9±1.3% was observed in GaAs directional couplers. Classical and quantum interference fringes with visibilities of 98.6±1.3% and 84.4±1.5% respectively were demonstrated in Mach-Zehnder interferometers exploiting the electro-optic Pockels effect. This work paves the way for a fully integrated quantum technology platform based on the GaAs material system.

  9. Enhanced photothermal conversion in vertically oriented gallium arsenide nanowire arrays.

    PubMed

    Walia, Jaspreet; Dhindsa, Navneet; Flannery, Jeremy; Khodabad, Iman; Forrest, James; LaPierre, Ray; Saini, Simarjeet S

    2014-10-01

    The photothermal properties of vertically etched gallium arsenide nanowire arrays are examined using Raman spectroscopy. The nanowires are arranged in square lattices with a constant pitch of 400 nm and diameters ranging from 50 to 155 nm. The arrays were illuminated using a 532 nm laser with an incident energy density of 10 W/mm(2). Nanowire temperatures were highly dependent on the nanowire diameter and were determined by measuring the spectral red-shift for both TO and LO phonons. The highest temperatures were observed for 95 nm diameter nanowires, whose top facets and sidewalls heated up to 600 and 440 K, respectively, and decreased significantly for the smaller or larger diameters studied. The diameter-dependent heating is explained by resonant coupling of the incident laser light into optical modes of the nanowires, resulting in increased absorption. Photothermal activity in a given nanowire diameter can be optimized by proper wavelength selection, as confirmed using computer simulations. This demonstrates that the photothermal properties of GaAs nanowires can be enhanced and tuned by using a photonic lattice structure and that smaller nanowire diameters are not necessarily better to achieve efficient photothermal conversion. The diameter and wavelength dependence of the optical coupling could allow for localized temperature gradients by creating arrays which consist of different diameters. PMID:25233265

  10. Ductile alloy and process for preparing composite superconducting wire

    DOEpatents

    Verhoeven, John D. (Ames, IA); Finnemore, Douglas K. (Ames, IA); Gibson, Edwin D. (Ames, IA); Ostenson, Jerome E. (Ames, IA)

    1983-03-29

    An alloy for the commercial production of ductile superconducting wire is prepared by melting together copper and at least 15 weight percent niobium under non-oxygen-contaminating conditions, and rapidly cooling the melt to form a ductile composite consisting of discrete, randomly distributed and orientated dendritic-shaped particles of niobium in a copper matrix. As the wire is worked, the dendritric particles are realigned parallel to the longitudinal axis and when drawn form a plurality of very fine ductile superconductors in a ductile copper matrix. The drawn wire may be tin coated and wound into magnets or the like before diffusing the tin into the wire to react with the niobium. Impurities such as aluminum or gallium may be added to improve upper critical field characteristics.

  11. Defect behavior in electron-irradiated boron- and gallium-doped silicon

    NASA Technical Reports Server (NTRS)

    Drevinsky, P. J.; Deangelis, H. M.

    1982-01-01

    Production and anneal of defects in electron-irradiated, float-zone silicon solar cells were studied by DLTS. In boron- and gallium-doped, n+-p cells, dominant defects were due to the divacancy, carbon interstitial, and carbon complex. Results suggest that the DLTS peak normally ascribed to carbon complexes also involves gallium. For gallium- and, to a lesser extent, boron-doped samples, damaged lifetime shows substantial recovery only when the carbon-complex peak has annealed out at 400 C. In boron-doped, n+-p-p+ cells, a minority carrier trap (E1) was also observed by DLTS in cells with a boron p+, but not in those with an aluminum p+ back. A level at Ev + 0.31 eV appeared upon 150 C annealing (E1 out) in both p+ back types of samples.

  12. Synthesis and Characterization of Cationic Low-Valent Gallium Complexes of Cryptand[2.2.2].

    PubMed

    Bourque, Jeremy L; Boyle, Paul D; Baines, Kim M

    2015-06-26

    The synthesis and characterization of two bimetallic, cationic low-valent gallium-cryptand[2.2.2] complexes is reported. The reaction of cryptand[2.2.2] with Ga2 Cl4 gave two different cations, [Ga3 Cl4 (crypt-222)](+) (1) or [Ga2 Cl2 (crypt-222)](2+) (2), depending on whether or not trimethylsilyl triflate (Me3 SiOTf) was added as a co-reagent. Complexes 1 and 2 are the first examples of bimetallic cryptand[2.2.2] complexes, as well as the first low-valent gallium-cryptand[2.2.2] complexes. Computational methods were used to evaluate the bonding in the gallium cores. PMID:26037242

  13. Demonstration of surface-enhanced Raman scattering by tunable, plasmonic gallium nanoparticles

    PubMed Central

    Wu, Pae C; Khoury, Christopher G.; Kim, Tong-Ho; Yang, Yang; Losurdo, Maria; Bianco, Giuseppe V.; Vo-Dinh, Tuan; Brown, April S.; Everitt, Henry O.

    2009-01-01

    Size-controlled gallium nanoparticles deposited on sapphire are explored as alternative substrates to enhance Raman spectral signatures. Gallium’s resilience following oxidation is inherently advantageous compared to silver for practical ex vacuo, non-solution applications. Ga nanoparticles are grown using a simple, molecular beam epitaxy-based fabrication protocol, and by monitoring their corresponding surface plasmon resonance energy through in situ spectroscopic ellipsometry, the nanoparticles are easily controlled for size. Raman spectroscopy performed on cresyl fast violet (CFV) deposited on substrates of differing mean nanoparticle size represents the first demonstration of enhanced Raman signals from reproducibly tunable self-assembled Ga nanoparticles. Non-optimized aggregate enhancement factors of ~80 were observed from the substrate with the smallest Ga nanoparticles for CFV dye solutions down to a dilution of 10 ppm. PMID:19655747

  14. Influence of Gallium Sources on Impurity Doping in Gas Source MBE GaAs

    NASA Astrophysics Data System (ADS)

    Misawa, Shunji; Okumura, Hajime; Yoshida, Sadafumi

    1987-07-01

    The difference of gallium sources, elemental gallium (Ga) and triethylgallium (TEG) on impurity doping in GaAs grown by gas source MBE using AsH3 gas has been studied. Unintentionally doped GaAs epilayers show p- and n-type conductivities, respectively, with and without a Liq.N2 trap in oil diffusion pump evacuation system when TEG was used as a gallium source. On the other hand, all the GaAs epilayers grown using Ga show p-type conductivity. Si doping efficiency by use of SiH4 gas for the growth using TEG is about 6-times higher than that for growth using Ga. The differences of impurity doping in gas source MBE using TEG and Ga are discussed based on the results of photoluminescence and secondary ion mass spectroscopic measurements.

  15. Crystal chemistry and self-lubricating properties of monochalcogenides gallium selenide and tin selenide

    SciTech Connect

    Erdemir, A.

    1993-02-01

    This paper describes the fundamentals of the crystal chemistry and self-lubricating mechanisms of two monochalcogenides; tin selenide and gallium selenide. Specifically, it enumerates their inter-atomic array and bond structure in crystalline states, and correlates this fundamental knowledge with their self-lubricating capacity. Friction tests assessing the self-lubricating performance of gallium and tin selenides were carried out on a pin-on-disk machine. Specifically, large crystalline pieces of gallium selenide and tin selenide were cut and cleaved into flat squares and subsequently rubbed against the sapphire balls. In another case, the fine powders (particle size {approx} 50--100 {mu}m) of gallium selenide and tin selenide were manually fed into the sliding interfaces of 440C pins and 440C disks. For the specific test conditions explored, it was found that the friction coefficients of the sapphire/gallium selenide and sapphire/tin selenide pairs were {approx} 0.23 and {approx} 0.35, respectively. The friction coefficients of 440C pin/440C disk test pairs with gallium selenide and tin selenide powders were on the orders of {approx} 0.22 and {approx} 0.38, respectively. For comparison, a number of parallel friction tests were performed with MoS{sub 2} powders and compacts and the results of these tests were also reported. The friction data together with the crystal-chemical knowledge and the electron microscopic evidence supported the conclusion that the lubricity and self-lubricating mechanisms of these solids are closely related to their crystal chemistry and the nature of interlayer bonding.

  16. The comparison between gallium arsenide and indium gallium arsenide as materials for solar cell performance using Silvaco application

    NASA Astrophysics Data System (ADS)

    Zahari, Suhaila Mohd; Norizan, Mohd Natashah; Mohamad, Ili Salwani; Osman, Rozana Aina Maulat; Taking, Sanna

    2015-05-01

    The work presented in this paper is about the development of single and multilayer solar cells using GaAs and InGaAs in AM1.5 condition. The study includes the modeling structure and simulation of the device using Silvaco applications. The performance in term of efficiency of Indium Gallium Arsenide (InGaAs) and GaAs material was studied by modification of the doping concentration and thickness of material in solar cells. The efficiency of the GaAs solar cell was higher than InGaAs solar cell for single layer solar cell. Single layer GaAs achieved an efficiency about 25% compared to InGaAs which is only 2.65% of efficiency. For multilayer which includes both GaAs and InGaAs, the output power, Pmax was 8.91nW/cm² with the efficiency only 8.51%. GaAs is one of the best materials to be used in solar cell as a based compared to InGaAs.

  17. Ohmic contact formation process on low n-type gallium arsenide (GaAs) using indium gallium zinc oxide (IGZO)

    SciTech Connect

    Yang, Seong-Uk [Samsung-SKKU Graphene Center and School of Electronics and Electrical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Product and Test Engineering Team, System LSI Division, Samsung Electronics Co., Ltd, Yongin 446-711 (Korea, Republic of); Jung, Woo-Shik [Department of Electrical Engineering, Stanford University, Stanford, CA 94305 (United States); Lee, In-Yeal; Jung, Hyun-Wook; Kim, Gil-Ho [Samsung-SKKU Graphene Center and School of Electronics and Electrical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Park, Jin-Hong, E-mail: jhpark9@skku.edu [Samsung-SKKU Graphene Center and School of Electronics and Electrical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2014-02-01

    Highlights: • We propose a method to fabricate non-gold Ohmic contact on low n-type GaAs with IGZO. • 0.15 A/cm{sup 2} on-current and 1.5 on/off-current ratio are achieved in the junction. • InAs and InGaAs formed by this process decrease an electron barrier height. • Traps generated by diffused O atoms also induce a trap-assisted tunneling phenomenon. - Abstract: Here, an excellent non-gold Ohmic contact on low n-type GaAs is demonstrated by using indium gallium zinc oxide and investigating through time of flight-secondary ion mass spectrometry, X-ray photoelectron spectroscopy, transmission electron microscopy, J–V measurement, and H [enthalpy], S [entropy], Cp [heat capacity] chemistry simulation. In is diffused through GaAs during annealing and reacts with As, forming InAs and InGaAs phases with lower energy bandgap. As a result, it decreases the electron barrier height, eventually increasing the reverse current. In addition, traps generated by diffused O atoms induce a trap-assisted tunneling phenomenon, increasing generation current and subsequently the reverse current. Therefore, an excellent Ohmic contact with 0.15 A/cm{sup 2} on-current density and 1.5 on/off-current ratio is achieved on n-type GaAs.

  18. Effect of magnetic field on the mechanical properties of magnetostrictive iron-gallium nanowires

    SciTech Connect

    Downey, Patrick R.; Flatau, Alison B. [Department of Aerospace Engineering, University of Maryland, 3181 Martin Hall, College Park, Maryland 20742 (United States); McGary, Patrick D.; Stadler, Bethanie J. H. [Department of Electrical and Computer Engineering, University of Minnesota, 200 Union St., Minneapolis, Minnesota 55455 (United States)

    2008-04-01

    This study experimentally investigates the elastic properties of individual iron-gallium nanowires with and without an applied magnetic bias field. The experiments were conducted with a custom manipulator stage designed for use within a scanning electron microscope, where nanowires were mechanically tested both statically and dynamically. Experiments were also performed in the presence of a 20 Oe dc magnetic field in order to identify any variation in wire properties. The results suggest that iron-gallium nanowires possess an elastic modulus very similar to the macroscale value, tensile strengths of more than double the bulk material, and minor magnetic field induced stiffening at low stresses.

  19. Thermal Cycling and High Temperature Reverse Bias Testing of Control and Irradiated Gallium Nitride Power Transistors

    NASA Technical Reports Server (NTRS)

    Patterson, Richard L.; Boomer, Kristen T.; Scheick, Leif; Lauenstein, Jean-Marie; Casey, Megan; Hammoud, Ahmad

    2014-01-01

    The power systems for use in NASA space missions must work reliably under harsh conditions including radiation, thermal cycling, and exposure to extreme temperatures. Gallium nitride semiconductors show great promise, but information pertaining to their performance is scarce. Gallium nitride N-channel enhancement-mode field effect transistors made by EPC Corporation in a 2nd generation of manufacturing were exposed to radiation followed by long-term thermal cycling and testing under high temperature reverse bias conditions in order to address their reliability for use in space missions. Result of the experimental work are presented and discussed.

  20. The clinical significance of radionuclide bone and gallium scanning in osteomyelitis of the head and neck

    SciTech Connect

    Noyek, A.M.; Kirsh, J.C.; Greyson, N.D.; Wortzman, G.; Jazrawy, H.; Freeman, J.L.; Blair, R.L.; Chapnik, J.S.

    1984-05-01

    Osteomyelitis of the head and neck remains a difficult clinical problem both in diagnosis and treatment evaluation. The purpose of this manuscript is to review our clinical experience with 25 cases of osteomyelitis distributed evenly among the temporal bone and skull base, the paranasal sinuses, and the mandible. Radionuclide bone and gallium scan images accurately depicted the biologic activity of the disease process and permitted accurate treatment evaluation and patient monitoring. This work demonstrates the potentials and limitations of radionuclide imaging with bone and gallium scan agents and attempts to define a role for their contemporary use in the management of osteomyelitis of the head and neck.

  1. Results of the Gallium-Clad Phase 3 and Phase 4 tasks (canceled prior to completion)

    SciTech Connect

    Morris, R.N.

    1998-08-01

    This report summarizes the results of the Gallium-Clad interactions Phase 3 and 4 tasks. Both tasks were to involve examining the out-of-pile stability of residual gallium in short fuel rods with an imposed thermal gradient. The thermal environment was to be created by an electrical heater in the center of the fuel rod and coolant flow on the rod outer cladding. Both tasks were canceled due to difficulties with fuel pellet fabrication, delays in the preparation of the test apparatus, and changes in the Fissile Materials Disposition program budget.

  2. Weldability of intermetallic alloys

    SciTech Connect

    David, S.A. (Oak Ridge National Lab., TN (United States))

    1990-01-01

    Ordered intermetallic alloys are a unique class of material that have potential for structural applications at elevated temperatures. The paper describes the welding and weldability of these alloys. The alloys studied were nickel aluminide (Ni[sub 3]Al), titanium aluminide (Ti[sub 3]Al), and iron aluminide.

  3. Alloy phase diagrams

    Microsoft Academic Search

    L. H. Bennett; B. C. Giessen; T. B. Massalski

    1984-01-01

    These proceedings collect papers presented at a symposium on alloy phase diagrams. Topics include: Crystal phase transformations; order-disorder transformations; crystal lattices; metallic glasses; metastable states; solubility; binary alloy systems; and alloys of iron, tantalum, silicon, aluminum, germanium, palladium, copper, and nickel.

  4. Alloys for aerospace

    Microsoft Academic Search

    S. Tuominen; C. Wojcik

    1995-01-01

    Aerospace industries require special allows with many properties tailored to meet specific needs. Prerequisites include clean melting techniques to maintain low impurity levels, tight control of alloy chemistry, and the analytical capability to characterize the product. Teledyne Wah Chang (TWC) produces specially refractory metals, including zirconium, hafnium, titanium, niobium and vanadium, which are essential components of many aerospace alloys. Alloys

  5. Calculation of Gallium-metal-Arsenic phase diagrams

    NASA Technical Reports Server (NTRS)

    Scofield, J. D.; Davison, J. E.; Ray, A. E.; Smith, S. R.

    1991-01-01

    Electrical contacts and metallization to GaAs solar cells must survive at high temperatures for several minutes under specific mission scenarios. The determination of which metallizations or alloy systems that are able to withstand extreme thermal excursions with minimum degradation to solar cell performance can be predicted by properly calculated temperature constitution phase diagrams. A method for calculating a ternary diagram and its three constituent binary phase diagrams is briefly outlined and ternary phase diagrams for three Ga-As-X alloy systems are presented. Free energy functions of the liquid and solid phase are approximated by the regular solution theory. Phase diagrams calculated using this method are presented for the Ga-As-Ge and Ga-As-Ag systems.

  6. Millimeter wave ferromagnetic resonance in gallium-substituted ?-iron oxide

    SciTech Connect

    Chao, Liu, E-mail: liu.chao@tufts.edu; Afsar, Mohammed N. [Department of Electrical and Computer Engineering, Tufts University, Medford, Massachusetts 02155 (United States); Ohkoshi, Shin-ichi [Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

    2014-05-07

    In millimeter wave frequency range, hexagonal ferrites with high uniaxial anisotropic magnetic fields are used as absorbers. These ferrites include M-type barium ferrite (BaFe{sub 12}O{sub 19}) and strontium ferrite (SrFe{sub 12}O{sub 19}), which have natural ferromagnetic resonant frequency range from 40 GHz to 60?GHz. However, the higher frequency range lacks suitable materials that support the higher frequency ferromagnetic resonance. A new series of gallium-substituted ?-iron oxides (?-Ga{sub x}Fe{sub 2?x}O{sub 3}) are synthesized which have ferromagnetic resonant frequencies appearing over the frequency range 30 GHz–150 GHz. The ?-Ga{sub x}Fe{sub 2?x}O{sub 3} is synthesized by the combination of reverse micelle and sol-gel techniques or the sol-gel method only. The particle sizes are observed to be smaller than 100 nm. In this paper, the free space magneto-optical approach has been employed to study these newly developed ?-Ga{sub x}Fe{sub 2?x}O{sub 3} particles in millimeter waves. This technique enables to obtain precise transmission spectra to determine the dielectric and magnetic properties of both isotropic and anisotropic ferrites in the millimeter wave frequency range from a single set of direct measurements. The transmittance and absorbance spectra of ?-Ga{sub x}Fe{sub 2?x}O{sub 3} are shown in this paper. Strong ferromagnetic resonances at different frequencies determined by the x parameter are found.

  7. Phase-change activities on gallium-doped indium oxide

    NASA Astrophysics Data System (ADS)

    Wang, S.-L.; Peng, L.-H.

    2010-10-01

    This study investigated the phase-change activities on a gallium-doped indium oxide (Ga:InO) device that can be supplied with a constant heat flow via symmetric contact to a pair of rodlike heating elements. A device set/reset current of 0.8/18 ?A and resistance window of 2.6×105 to 107 ? can be found on Ga:InO with a 6.2 ?m2 device area and a thickness of 40 nm. Analysis of a log-log plot revealed slopes of 1.07±0.01 and -1.12±0.03 that were found to correlate with the switching current and resistance change between the high-/low-value states of the Ga:InO device area, respectively. These observations lead to the estimated energy densities of 1.77±0.11 pJ/?m3 and 7.26±0.44 pJ/?m3 required to initiate the set and reset process in Ga:InO, respectively. Through differential scanning calorimetry analysis and acceleration tests of the Ga:InO film and the device, an activation energy of ˜1.275±0.005 eV was found, which corresponded to the high-/low-resistance state change. A data retention time of ten years was further estimated when the Ga:InO device is operated at 75 °C. According to the transmission electron microscopy analysis, these observations are correlated with an amorphous to cubic phase transition in In2O3, which takes place at a crystallization temperature of 252 °C, and suggest that the phase-change activities originate from the Joule heating effect.

  8. Gallium-cladding compatibility testing plan: Phase 3 -- Test plan for centrally heated surrogate rodlet test. Revision 2

    SciTech Connect

    Morris, R.N.; Baldwin, C.A.; Wilson, D.F.

    1998-07-01

    The Fissile Materials Disposition Program (FMDP) is investigating the use of weapons grade plutonium in mixed oxide (MOX) fuel for light-water reactors (LWR). Commercial MOX fuel has been successfully used in overseas reactors for many years; however, weapons derived fuel may differ from the previous commercial fuels because of small amounts of gallium impurities. A concern presently exists that the gallium may migrate out of the fuel, react with and weaken the clad, and thereby promote loss of fuel pin integrity. Phases 1 and 2 of the gallium task are presently underway to investigate the types of reactions that occur between gallium and clad materials. This is a Level-2 document as defined in the Fissile Materials Disposition Program Light-Water Reactor Mixed-Oxide Fuel Irradiation Test Project Plan. This Plan summarizes the projected Phase 3 Gallium-Cladding compatibility heating test and the follow-on post test examination (PTE). This work will be performed using centrally-heated surrogate pellets, to avoid unnecessary complexities and costs associated with working with plutonium and an irradiation environment. Two sets of rodlets containing pellets prepared by two different methods will be heated. Both sets will have an initial bulk gallium content of approximately 10 ppm. The major emphasis of the PTE task will be to examine the material interactions, particularly indications of gallium transport from the pellets to the clad.

  9. Solidification of undercooled Fe-Cr-Ni alloys. Part 3: Phase selection in chill casting

    SciTech Connect

    Koseki, Toshihiko; Flemings, M.C. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Materials Science and Engineering

    1997-11-01

    In Parts 1 and 2 of this series of articles, it was shown that a range of levitation-melted Fe-Cr-Ni alloys, both hypoeutectic and hypereutectic, all solidified with the hypereutectic phase (bcc) as their primary phase, except for the hypoeutectic alloys at low undercoolings. In this article, the effect of heat extraction on phase formation is studied by chill casting the undercooled alloys before nucleation. Two of the previously studied alloys are examined; one hypoeutectic and the other hypereutectic. Chill substrates employed were copper, stainless steel, alumina, zirconia, and a liquid gallium-indium bath. Contrary to the case of levitation melting and solidification, it is found that the dominant primary phase to solidify in both alloys, independent of chill substrate, is the hypoeutectic phase (fcc). It is concluded that chilling the undercooled melt results in nearly concurrent nucleation of bcc and fcc. Two different mechanisms are considered as possible explanations of the subsequent fcc phase selection during growth. These are termed growth velocity and phase stability mechanisms. Evidence favors a phase stability mechanism, in which the bcc phase massively transforms to fcc early in solidification to that fcc then grows without competition. It is suggested that this mechanism may also explain structures observed in welds and other rapid solidification processes.

  10. Single-Crystal NiAl-X Alloys Tested for Hot Corrosion

    NASA Technical Reports Server (NTRS)

    Nesbitt, James A.

    1999-01-01

    Single-crystal nickel aluminide (NiAl) has been investigated extensively throughout the last several years as a potential structural material in aero-gas turbine engines. The attractive features of NiAl in comparison to Ni-base superalloys include a higher melting point, lower density, higher thermal conductivity, and excellent oxidation resistance. However, NiAl suffers from a lack of ductility and fracture toughness at low temperatures and a low creep strength at high temperatures. Alloying additions of hafnium (Hf), gallium (Ga), titanium (Ti), and chromium (Cr) have each shown some benefit to the mechanical properties over that of the binary alloy. However, the collective effect of these alloying additions on the environmental resistance of NiAl-X was unclear. Hence, the present study was undertaken to examine the hot corrosion behavior of these alloys. A companion study examined the cyclic oxidation resistance of these alloys. Several single-crystal NiAl-X alloys (where X is Hf, Ti, Cr, or Ga) underwent hot corrosion testing in a Mach 0.3 burner rig at the NASA Lewis Research Center. Samples were tested for up to 300 1-hr cycles at a temperature of 900 C. It was found that increasing the Ti content from 1 to 5 at.% degraded the hot corrosion behavior. This decline in the behavior was reflected in high weight gains and large corrosion mound formation during testing (see the figures). However, the addition of 1 to 2 at.% Cr to alloys containing 4 to 5 at.% Ti appeared to greatly reduce the susceptibility of these alloys to hot corrosion attack and negated the deleterious effect of the increased Ti addition.

  11. High strength alloys

    DOEpatents

    Maziasz, Phillip James [Oak Ridge, TN; Shingledecker, John Paul [Knoxville, TN; Santella, Michael Leonard [Knoxville, TN; Schneibel, Joachim Hugo [Knoxville, TN; Sikka, Vinod Kumar [Oak Ridge, TN; Vinegar, Harold J [Bellaire, TX; John, Randy Carl [Houston, TX; Kim, Dong Sub [Sugar Land, TX

    2010-08-31

    High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tubular that is at least partially made from a material containing at least one of the metal alloys.

  12. Gallium and indium co-doping of epitaxial zinc oxide thin films grown in water at 90 °C

    Microsoft Academic Search

    Hong Quang Le; Soo Jin Chua

    2011-01-01

    Zinc oxide (ZnO) thin films were intentionally co-doped with group III elements (gallium) in order to investigate and understand the effects of co-doping on the morphological, electrical and optical properties of gallium-doped ZnO (GZO) films. The co-doped films were grown on MgAl2O4 spinel substrates using a low-temperature solution-phase method known as hydrothermal synthesis. Gallium with indium co-doped ZnO (GIZO) films

  13. Polyaniline\\/gallium doped ZnO heterostructure device via plasma enhanced polymerization technique: Preparation, characterization and electrical properties

    Microsoft Academic Search

    Sadia Ameen; M. Shaheer Akhtar; Young Soon Kim; O-Bong Yang; Hyung-Shik Shin

    2011-01-01

    The ZnO and gallium-doped ZnO nanoparticles (NPs) were synthesized by simple chemical method and used for the fabrication\\u000a of p-polyaniline\\/n-ZnO heterostructures devices in which polyaniline was deposited by plasma-enhanced polymerization. The\\u000a increment in the crystallite sizes of gallium doped ZnO nanoparticles from ~21.85 nm to ~32.39 nm indicated the incorporation\\u000a of gallium ion into the ZnO nanoparticles. The surface and structural studies

  14. Chemical vapor deposition of aluminum and gallium nitride thin films from metalorganic precursors

    E-print Network

    Economou, Demetre J.

    . The barrier properties of the aluminum nitride films in a Si/AlN/Au metallization scheme were examined Society. I. INTRODUCTION Aluminum nitride has a large direct band gap of 6.2 eV, high thermal conductivityChemical vapor deposition of aluminum and gallium nitride thin films from metalorganic precursors

  15. Gallium arsenide integrated optical devices for high-speed diagnostic systems

    SciTech Connect

    McWright, G.; Lowry, M.; Takeuchi, E.; Murphy, G.; Tindall, W.; Koo, J.; Roeske, F.

    1987-01-01

    The design, fabrication, and evaluation of waveguide electro-optic modulators in gallium arsenide for application to high-speed diagnostic systems are discussed specifically. This paper is focused on high bandwidth, single event analog modulation, and radiation susceptibility of these devices.

  16. Layer by layer nanoassembly of copper indium gallium selenium (CIGS) nanoparticles for solar cell application

    Microsoft Academic Search

    Azadeh Hemati

    2011-01-01

    In this research thesis, copper indium gallium selenium (CIGS) nanoparticles were synthesized from metal chlorides, functionalized to disperse in water, and further used in layer by layer (LbL) nanoassembly of CIGS films. CIGS nanoparticles were synthesized through the colloidal precipitation in an organic solvent. The peak and average sizes of the synthesized particles were measured to be 68 nm and

  17. Transient response of gallium arsenide and silicon solar cells under laser pulse

    Microsoft Academic Search

    Raj K. Jain; G. A. Landis

    1994-01-01

    Solar cells can be used as receivers in laser power beaming applications. Power beamed to a photovoltaic array could power a satellite, an orbital transfer vehicle or a lunar base. Understanding solar cell response to the pulsed output of a free-electron laser (FEL) is important for evaluation of power-beaming applications. In this work we investigate the time response of gallium

  18. Gallium citrate Ga 67 accumulation in pulmonary lesions after chemotherapy (MOPP)

    SciTech Connect

    Wells, J.D.; Huskison, W.T.; Davenport, O.L.

    1986-10-01

    We have described a patient with Hodgkin's disease who had fever and pulmonary infiltrates after treatment with mantle x-ray therapy and two courses of MOPP. Gallium affinity of the lung lesions proved at biopsy not to be due to Hodgkin's disease, but probably to chemotherapy-induced pulmonary toxicity.

  19. Residual mediastinal mass in malignant lymphoma: value of magnetic resonance imaging and gallium scan.

    PubMed

    Brice, P; Rain, J D; Frija, J; Miaux, Y; Marolleau, J P; Tredaniel, J; Ferme, C; Hennequin, C; Gisselbrecht, C

    1993-08-01

    Following treatment for mediastinal lymphoma, residual masses are defined as a mass greater than 2 cm observed on the CT scan in the absence of other evolutive signs of lymphoma. In this study, we examined 55 patients with residual mediastinal mass after optimal therapy, using gallium scan (37 cases) or magnetic resonance imaging (MRI, 44 cases). The group comprised 41 subjects with Hodgkin's disease and 14 with non Hodgkin's lymphoma, stages I and II (32 cases) and stages III and IV (23 cases); 35 subjects (64%) having bulky mediastinal involvement at diagnosis. A negative gallium scan or fibrotic signal on MRI was correlated with complete remission in 48 cases (87%). In seven of these 48 patients, MRI was not conclusive with a high signal of indeterminate tissue following radiotherapy, but four of the seven had fibrotic tissue on biopsy and none relapsed. Positive gallium scan was observed in six cases. In conclusion, we suggest performing a gallium scan at the end of induction chemotherapy and when it is negative, treatment may be continued without surgical biopsy or salvage therapy. MRI is of value when it shows fibrotic tissue but can be inconclusive. PMID:8414967

  20. Investigation of orientational anisotropic scattering in neutron-irradiated gallium arsenide (GaAs)

    Microsoft Academic Search

    M. R. Baig

    1995-01-01

    A single crystal of gallium arsenide was irradiated with a total dose of 9 × 1019 neutrons cm?2 by fast neutrons in the reactor of Atomic Energy Centre, Aldermaston, UK, at a temperature of 40 °C. The small angle neutron scattering from irradiated and unirradiated samples was measured under identical conditions at the Institute Laue Langevin, France, using a D11

  1. Dispersion data for open suspended microstrip on Alumina and Gallium Arsenide substrates

    NASA Astrophysics Data System (ADS)

    Tomar, R. S.; Bhartia, Prakash

    1988-01-01

    Accurate dispersion data for open suspended microstrop on RT-duroid and fused quartz substrates was presented in an earlier paper by the authors. The present work repeats the same exercise for two more commonly used substrate materials, namely, Alumina and Gallium Arsenide. The results are new and will be a very useful addition to the millimeter-wave circuit designer's library.

  2. Electron Scattering by Neutralized Acceptors in Germanium. I. Gallium and Indium

    Microsoft Academic Search

    Eizo Otsuka; Kazuo Murase; Jiro Iseki

    1966-01-01

    It is shown that the well-known Erginsoy's formula for scattering of electrons by neutral impurity is not valid for the electron scattering by neutralized acceptors in germanium or silicon. An alternative formula based on the positron-hydrogen scattering picture is presented and compared with the cyclotron resonance observation of the electron scattering by gallium and indium atoms in germanium. From the

  3. The performance of gallium arsenide\\/germanium solar cells at the Martian surface

    Microsoft Academic Search

    D. Crisp; A. Pathare; R. C. Ewell

    2004-01-01

    A theoretical model was used to predict the electrical power output by Gallium Arsenide\\/ Germanium solar cells at the surface of Mars. This model was validated using measurements from the Mars Pathfinder Lander. It was then used to estimate the solar power output as a function of latitude, local time, and season for airborne dust optical depths between 0.1 and

  4. Fabrication of Indium Gallium Zinc Oxide (IGZO) TFTs Using a Solution-Based Process

    Microsoft Academic Search

    Mi Sun Park; Doo Hyoung Lee; Eun Jin Bae; Dae-Hwan Kim; Jin Gyu Kang; Dae-Ho Son; Si Ok Ryu

    2010-01-01

    Highly transparent (?90% in the visible region) indium gallium zinc oxide (IGZO) thin films were deposited using a spin coating process with a newly developed precursor solution. Acetonitrile was used as the solvent in the preparation of the metal halide precursor solution for the deposition of the IGZO thin films. Ethylene glycol was added to the solvent at four different

  5. Gallium nitride based microcavity light emitting diodes with 2lambda effective cavity thickness

    Microsoft Academic Search

    P. Morgan Pattison; Aurelien David; Rajat Sharma; Claude Weisbuch; Steven Denbaars; Shuji Nakamura

    2007-01-01

    Gallium nitride based microcavity light emitting diodes less than 400 nm thick emitting at a peak wavelength of 455 nm have been fabricated. The epitaxial structure was grown by metal organic chemical vapor deposition, and the device was fabricated using a laser lift-off process. Cavity thinning was carried out using inductively coupled plasma etching until a cavity length of roughly

  6. Separation of Gallium and Indium Isotopes by Cation and Anion Exchange Chromatography

    Microsoft Academic Search

    I. Herdzik; W. Dembi?ski; J. Narbutt; S. Siekierski

    2012-01-01

    Ion exchange chromatography was applied to study chemical isotope effects of gallium and indium in ligand exchange reactions. Strongly acidic cation and strongly basic anion exchange resin were used as a solid phase, and aqueous HCl as a liquid phase. On the cation exchanger, the light isotope Ga was enriched at the front part of the elution band and the

  7. Two years of on-orbit gallium arsenide performance from the LIPS solar cell panel experiment

    Microsoft Academic Search

    R. W. Francis; F. E. Betz

    1985-01-01

    The LIPS on-orbit performance of the gallium arsenide panel experiment was analyzed from flight operation telemetry data. Algorithms were developed to calculate the daily maximum power and associated solar array parameters by two independent methods. The first technique utilizes a least mean square polynomial fit to the power curve obtained with intensity and temperature corrected currents and voltages; whereas, the

  8. Direct observation of copper depletion and potential changes at copper indium gallium diselenide grain boundaries

    Microsoft Academic Search

    M. J. Hetzer; Y. M. Strzhemechny; M. Gao; M. A. Contreras; A. Zunger; L. J. Brillson

    2005-01-01

    We have used micro-Auger electron spectroscopy, cathodoluminescence spectroscopy, and work function measurements in copper indium gallium diselenide polycrystalline solar cell films cleaved in ultrahigh vacuum. We establish that, relative to the grain interior, the grain boundary shows (1) a Cu composition decrease, as large as a factor of two, (2) a work function decrease of up to 480 meV, and

  9. Gallium-67 breast uptake in a patient with hypothalamic granuloma (sarcoid)

    SciTech Connect

    Vazquez, R.; Oates, E.; Sarno, R.C.; Fay, J.; Gale, D.R.

    1988-01-01

    An unusual case is presented of bilateral breast uptake of (/sup 67/Ga)citrate in a patient with a hypothalamic granuloma in the absence of galactorrhea is presented. A possible mechanism for this incidental finding is elevated prolactin levels, as other causes of gallium breast uptake such as drug therapy, and intrinsic breast disease, were not present.

  10. Alloying of aluminum-beryllium alloys

    NASA Astrophysics Data System (ADS)

    Molchanova, L. V.; Ilyushin, V. N.

    2013-01-01

    The existing phase diagrams of Al-Be- X alloys, where X is an alloying element, are analyzed. Element X is noted to poorly dissolve in both aluminum and beryllium. It is shown that the absence of intermetallic compounds in the Al-Be system affects the phase equilibria in an Al-Be- X system. Possible phase equilibria involving phases based on aluminum, beryllium, and intermetallic compounds are proposed, and the types of strengthening of Al-Be alloys by an addition of a third element are classified.

  11. Development of titanium alloys by the method of complex alloying

    Microsoft Academic Search

    A. I. Khorev

    2006-01-01

    We study the effect of alloying on the mechanical properties of welded joints and base metal of titanium alloys of the system\\u000a Ti-Al-Mo-V-Cr-Fe. We also formulate the theoretical aspects and principles of complex alloying of titanium alloys and the\\u000a theory of alloying of additive materials for the welding of ?-, (? + ?), and ?-alloys. It has been shown that

  12. The design, construction, and testing of a nuclear fuel rod thermal simulation system to study gallium/Zircaloy interactions 

    E-print Network

    Allison, Christopher Curtis

    1999-01-01

    electric heaters, annular pellets of depleted uranium/cerium oxide doped with approximately 10 ppm of gallium, a small helium filled gap, and generic Zircaloy IV cladding. The system is controlled through a computer-based data acquisition system...

  13. Surface alloying of Mg alloys after surface nanocrystallization.

    PubMed

    Zhang, Ming-Xing; Shi, Yi-Nong; Sun, Haiqing; Kelly, Patrick M

    2008-05-01

    Surface nanocrystallization using a surface mechanical attrition treatment effectively activates the surface of magnesium alloys due to the increase in grain boundary diffusion channels. As a result, the temperature of subsequent surface alloying treatment of pure Mg and AZ91 alloy can be reduced from 430 degrees C to 380 degrees C. Thus, it is possible to combine the surface alloying process with the solution treatment for this type of alloy. After surface alloying, the hardness of the alloyed layer is 3 to 4 times higher than that of the substrate and this may significantly improve the wear resistance of magnesium alloys. PMID:18572716

  14. Uranium-titanium-niobium alloy

    Microsoft Academic Search

    Ludtka

    1990-01-01

    This patent describes a uranium alloy having small additions of Ti and Nb. It shows improved strength and ductility in cross-section of greater than one inch over prior uranium alloy having only Ti as an alloy element.

  15. Catalyst Alloys Processing

    NASA Astrophysics Data System (ADS)

    Tan, Xincai

    2014-10-01

    Catalysts are one of the key materials used for diamond formation at high pressures. Several such catalyst products have been developed and applied in China and around the world. The catalyst alloy most widely used in China is Ni70Mn25Co5 developed at Changsha Research Institute of Mining and Metallurgy. In this article, detailed techniques for manufacturing such a typical catalyst alloy will be reviewed. The characteristics of the alloy will be described. Detailed processing of the alloy will be presented, including remelting and casting, hot rolling, annealing, surface treatment, cold rolling, blanking, finishing, packaging, and waste treatment. An example use of the catalyst alloy will also be given. Industrial experience shows that for the catalyst alloy products, a vacuum induction remelt furnace can be used for remelting, a metal mold can be used for casting, hot and cold rolling can be used for forming, and acid pickling can be used for metal surface cleaning.

  16. Noise analysis of gallium arsenide pixel X-ray detectors coupled to ultra-low noise electronics

    Microsoft Academic Search

    G. Bertuccio; R. Casiraghi; D. Maiocchi; A. Owens; M. Bavdaz; A. Peacock; H. Andersson; S. Nenonen

    2003-01-01

    The X-ray spectroscopic performance and the noise analysis of gallium arsenide pixel detectors coupled to ultra-low noise front-end electronics is presented. The pixel junctions have areas of 200 × 200 ?m2 and they are fabricated on an epitaxial gallium arsenide layer 40 ?m thick. The front-end electronics consists of a forward bias field effect transistor amplifier with an equivalent noise

  17. Lymphocytic interstitial pneumonitis: a cause of pulmonary gallium-67 uptake in a child with acquired immunodeficiency syndrome

    SciTech Connect

    Zuckier, L.S.; Ongseng, F.; Goldfarb, C.R.

    1988-05-01

    Lymphocytic interstitial pneumonitis (LIP) is currently recognized as a frequent pediatric manifestation of the acquired immunodeficiency syndrome (AIDS). We report the gallium scan findings in a 3-yr-old girl with this disorder and review its clinical, radiologic, and pathologic features. LIP must be a prime consideration in the differential diagnosis of diffuse pulmonary gallium uptake in pediatric AIDS patients. Further experience will afford greater perspective on the diagnostic role that nuclear medicine will ultimately play in this disease. 49 references.

  18. Forward-biased current annealing of radiation-damaged gallium arsenide and silicon solar cells. Master's thesis

    Microsoft Academic Search

    Staats

    1987-01-01

    Radiation-damaged gallium arsenide and silicon solar cells were annealed using a combination of thermal and forward-bias current-annealing techniques. These cells were annealed under varying current densities from 0.125 to 1.250 A\\/sq. cm.2 and at temperatures from 90 to 140 C. Gallium arsenide solar cells annealed at current densities from 0.250 to 0.750 A\\/sq. cm. 2. Attempts to anneal silicon solar

  19. The 13.9 GHz short pulse radar noise figure measurements utilizing silicon and gallium-arsenide mixer diodes

    NASA Technical Reports Server (NTRS)

    Dombrowski, M.

    1977-01-01

    An analysis was made on two commercially available silicon and gallium arsenide Schottky barrier diodes. These diodes were selected because of their particularly low noise figure in the frequency range of interest. The specified noise figure for the silicon and gallium arsenide diodes were 6.3 db and 5.3 db respectively when functioning as mixers in the 13.6 GHz region with optimum local oscillator drive.

  20. Semiconductor alloy theory

    Microsoft Academic Search

    A. B. Chen

    1986-01-01

    This grant supported our work on semiconductor alloy theory. Many useful results have been obtained, including: (1) generalization of Brooks' formula for alloy-scattering limited electron mobility to including multiple bands and indirect gaps, (2) calculation of SiGe alloys band structure, electron-mobility and core-exciton binding energy and linewidth, (3) comprehensive calculation of bond energy, bond length and mixing enthalpy for all

  1. Low activation ferritic alloys

    DOEpatents

    Gelles, David S. (West Richland, WA); Ghoniem, Nasr M. (Granada Hills, CA); Powell, Roger W. (Pasco, WA)

    1986-01-01

    Low activation ferritic alloys, specifically bainitic and martensitic stainless steels, are described for use in the production of structural components for nuclear fusion reactors. They are designed specifically to achieve low activation characteristics suitable for efficient waste disposal. The alloys essentially exclude molybdenum, nickel, nitrogen and niobium. Strength is achieved by substituting vanadium, tungsten, and/or tantalum in place of the usual molybdenum content in such alloys.

  2. Amorphous metal alloy

    DOEpatents

    Wang, R.; Merz, M.D.

    1980-04-09

    Amorphous metal alloys of the iron-chromium and nickel-chromium type have excellent corrosion resistance and high temperature stability and are suitable for use as a protective coating on less corrosion resistant substrates. The alloys are stabilized in the amorphous state by one or more elements of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, and tungsten. The alloy is preferably prepared by sputter deposition.

  3. Measurement of Impact Ionization Coefficients in Gallium Nitride

    NASA Astrophysics Data System (ADS)

    Ozbek, Ayse Merve

    2011-12-01

    GaN has been recognized as a potential semiconductor for high temperature, high frequency and high power applications. Due to its wide bandgap, GaN exhibits high critical electric fields, which are suitable to sustain high breakdown voltages in power electronic devices. In order to obtain a good understanding of the breakdown characteristics of a power device, it is important to know the impact ionization coefficients of electrons and holes as a function of the electric field in the semiconductor. In this work, electron and hole impact ionization coefficients have been accurately measured in both GaN epitaxial layers grown on bulk GaN substrates and GaN epitaxial layers grown on Sapphire substrates using the pulsed electron beam induced current technique. Using Chynoweth's equation (alpha = a e-b/E), measurements for GaN epitaxial layer grown on bulk GaN substrates gave an aN value of 1.5x105 cm-1 and a bN value of 1.413x107 V/cm for the impact ionization coefficient of electrons in GaN at room temperature. For the impact ionization coefficients of holes in GaN, the values of aP and bP were found to be 6.4x105 cm-1 and 1.454x107 V/cm, respectively. An analytical solution of the form alpha = mEn for the variation of the impact ionization coefficients as a function of the electric field was derived, which is useful for analytical calculation of the breakdown voltages in GaN. For Chynoweth's equation (alpha = a e-b/E), measurements for GaN epitaxial layers grown on Sapphire substrates gave an aN value of 9.17x105 cm-1 and a bN value of 1.722x107 V/cm for the impact ionization coefficient for electrons at room temperature. For the impact ionization coefficients for holes at room temperature, the values of aP and bP were found to be 8.7x105 cm-1 and 1.464x107 V/cm, respectively. The values for both coefficients are larger than those measured for GaN grown on GaN substrates. The temperature dependence of the electron and hole impact ionization coefficients as a function of the electric field has been accurately measured for both GaN epitaxial layers grown on bulk GaN substrates and GaN epitaxial layers grown on Sapphire substrates. The impact ionization coefficients for both electrons and holes are observed to decrease with increasing temperature. This is consistent with the measured increase in the breakdown voltage with temperature for high voltage Schottky barrier diodes. This is an important observation demonstrating that stable power devices can be fabricated from Gallium Nitride. Electron Beam Induced Current (EBIC) technique was employed in order to understand the role of defects on the breakdown characteristics of GaN. The impact ionization coefficients for electrons and holes measured at the defective site were found to be higher than those measured at a non-defective site. These results indicate that the breakdown voltage of GaN devices can be reduced due to the presence of defects.

  4. High temperature ultrasonic transducers for imaging and measurements in a liquid Pb/Bi eutectic alloy.

    PubMed

    Kazys, Rymantas; Voleisis, Algirdas; Sliteris, Reimondas; Mazeika, Liudas; Van Nieuwenhove, Rudi; Kupschus, Peter; Abderrahim, Hamid Aït

    2005-04-01

    In some nuclear reactors or accelerator-driven systems (ADS) the core is intended to be cooled by means of a heavy liquid metal, for example, lead-bismuth (Pb/Bi) eutectic alloy. For safety and licensing reasons, an imaging method of the interior of ADS, based on application of ultrasonic waves, has thus to be developed. This paper is devoted to description of developed various ultrasonic transducers suitable for long term imaging and measurements in the liquid Pb/Bi alloy. The results of comparative experimental investigations of the developed transducers of different designs in a liquid Pb/Bi alloy up to 450 degrees C are presented. Prototypes with different high temperature piezoelectric materials were investigated: PZT, bismuth titanate (Bi4Ti3O12), lithium niobate (LiNbO3), gallium orthophosphate (GaPO4) and aluminum nitride (A1N). For acoustic coupling with the metal alloy, it was proposed to coat the active surface of the transducers by diamond like carbon (DLC). The radiation robustness was assessed by exposing the transducers to high gamma dose rates in one of the irradiation facilities at SCK x CEN. The experimental results proved that the developed transducers are suitable for long-term operation in harsh conditions. PMID:16060499

  5. Proof-of-Concept Experiments on a Gallium-Based Ignitron for Pulsed Power Applications

    NASA Technical Reports Server (NTRS)

    Ali, H. K.; Hanson, V. S.; Polzin, K. A.; Pearson, J. B.

    2015-01-01

    Ignitrons are electrical switching devices that operate at switching times that are on the order of microseconds, can conduct high currents of thousands of amps, and are capable of holding off tens of thousands of volts between pulses. They consist of a liquid metal pool within an evacuated tube that serves both the cathode and the source of atoms and electrons for an arc discharge. Facing the liquid metal pool is an anode suspended above the cathode, with a smaller ignitor electrode tip located just above the surface of the cathode. The ignitron can be charged to significant voltages, with a potential difference of thousands of volts between anode and cathode. When an ignition pulse is delivered from the ignitor electrode to the cathode, a small amount of the liquid metal is vaporized and subsequently ionized, with the high voltage between the anode and cathode causing the gas to bridge the gap between the two electrodes. The electrons and ions move rapidly towards the anode and cathode, respectively, with the ions liberating still more atoms from the liquid metal cathode surface as a high-current plasma arc discharge is rapidly established. This arc continues in a self-sustaining fashion until the potential difference between the anode and cathode drops below some critical value. Ignitrons have been used in a variety of pulsed power applications, including the railroad industry, industrial chemical processing, and high-power arc welding. In addition, they might prove useful in terrestrial power grid applications, serving as high-current fault switches, quickly shunting dangerous high-current or high-voltage spikes safely to ground. The motivation for this work stemmed from the fact that high-power, high-reliability, pulsed power devices like the ignitron have been used for ground testing in-space pulsed electric thruster technologies, and the continued use of ignitrons could prove advantageous to the future development and testing of such thrusters. Previous ignitron designs have used mercury as the liquid metal cathode, owing to its presence as a liquid at room temperatures and a vapor pressure of 10 Pa (75 mtorr) at room temperature. While these are favorable properties, there are obvious environmental and personal safety concerns with the storage, handling, and use of mercury and its compounds. The purpose of the present work was to fabricate and test an ignitron that used as its cathode an alternate liquid metal that was safe to handle and store. To that end, an ignitron test article that used liquid gallium as the cathode material was developed and tested. Gallium is a metal that has a melting temperature of 29.76 C, which is slightly above room temperature, and a boiling point of over 2,300 C at atmospheric pressure. This property makes gallium the element with the largest relative difference between melting and boiling points. Gallium has a limited role in biology, and when ingested, it will be subsequently processed by the body and expelled rather than accumulating to toxic levels. The next section of this Technical Memorandum (TM) provides background information on the development of mercury-based ignitrons, which serves as the starting point for the development of the gallium-based variant. Afterwards, the experimental hardware and setup used in proof-of-concept testing of a basic gallium ignitron are presented. Experimental data, consisting of discharge voltage and current waveforms as well as high-speed imaging of the gallium arc discharge in the gallium ignitron test article, are presented to demonstrate the efficacy of the concept. Discussion of the data and suggestions on improvements for future iterations of the design are presented in the final two sections of this TM.

  6. Fast neutron scattering on Gallium target at 14.8 MeV

    E-print Network

    Han, R; Chen, Z; Nie, Y; Liu, X; Zhang, S; Ren, P; Jia, B; Tian, G; Luo, F; Lin, W; Liu, J; Shi, F; Huang, M; Ruan, X; Ren, J; Zhou, Z; Huang, H; Bao, J; Zhang, K; Hu, B

    2014-01-01

    Benchmarking of evaluated nuclear data libraries was performed for $\\sim 14.8$ MeV neutrons on Gallium targets. The experiments were performed at China Institute of Atomic Energy(CIAE). Solid samples of natural Gallium (3.2 cm and 6.4 cm thick) were bombarded by $\\sim 14.8$ MeV neutrons and leakage neutron energy spectra were measured at 60$^{\\circ}$ and 120$^{\\circ}$. The measured spectra are rather well reproduced by MCNP-4C simulations with the CENDL-3.1, ENDF/B-VII and JENDL-4.0 evaluated nuclear data libraries, except for the inelastic contributions around $E_{n} = 10-13$ MeV. All three libraries significantly underestimate the inelastic contributions. The inelastic contributions are further studied, using the Talys simulation code and the experimental spectra are reproduced reasonably well in the whole energy range by the Talys calculation, including the inelastic contributions.

  7. Fast neutron scattering on Gallium target at 14.8 MeV

    NASA Astrophysics Data System (ADS)

    Han, R.; Wada, R.; Chen, Z.; Nie, Y.; Liu, X.; Zhang, S.; Ren, P.; Jia, B.; Tian, G.; Luo, F.; Lin, W.; Liu, J.; Shi, F.; Huang, M.; Ruan, X.; Ren, J.; Zhou, Z.; Huang, H.; Bao, J.; Zhang, K.; Hu, B.

    2015-04-01

    Benchmarking of evaluated nuclear data libraries was performed for ?14.8 MeV neutrons on Gallium targets. The experiments were performed at China Institute of Atomic Energy (CIAE). Solid samples of natural Gallium (3.2 cm and 6.4 cm thick) were bombarded by ?14.8 MeV neutrons and leakage neutron energy spectra were measured at 60°?and 120°. The measured spectra are rather well reproduced by MCNP-4C simulations with the CENDL3.1, ENDF/B-VII and JENDL-4.0 evaluated nuclear data libraries, except for the inelastic contributions around En = 10- 13 MeV. All three libraries significantly underestimate the inelastic contributions. The inelastic contributions are further studied, using the Talys simulation code and the experimental spectra are reproduced reasonably well in the whole energy range by the Talys calculation, including the inelastic contributions.

  8. Electrodeposition of Ga-O Thin Films from Aqueous Gallium Sulfate Solutions

    NASA Astrophysics Data System (ADS)

    Vequizo, Junie Jhon M.; Ichimura, Masaya

    2013-07-01

    Ga-O based thin films were electrodeposited on fluorine-doped tin oxide (FTO)-coated glass substrate at room temperature from aqueous gallium sulfate solution with hydrogen peroxide (H2O2). Effects of different deposition parameters such as deposition voltage, amount of H2O2 and deposition time were investigated and presented. Nearly smooth and crack-free morphologies were attained at -1.0 V vs SCE deposition potential. As-deposited films showed O to Ga ratio of 2.0, which signified GaOOH formation. Thermal annealing of the as-deposited films in ambient air at 500-600 °C reduced the O/Ga ratio closer to stoichiometric gallium oxide (Ga2O3) and retained the morphology of Ga-O thin films. As-prepared films with ˜0.2 µm thickness had 80% transparency in the visible wavelength range.

  9. Implications of Gallium Solar Neutrino Data for the Resonant Spin-Flavor Precession Scenario

    E-print Network

    E. Kh. Akhmedov; A. Lanza; S. T. Petcov

    1993-01-14

    We consider the implications of the recent results of SAGE and GALLEX experiments for the solution of the solar neutrino problem in the framework of the resonant neutrino spin-flavor precession scenario. It is shown that this scenario is consistent with all the existing solar neutrino data including the gallium results. The quality of the fit of the data depends crucially on the magnetic field profile used which makes it possible to get information about the magnetic field in the solar interior. In particular, the magnetic field in the core of the sun must not be too strong ($<3 \\times 10^6$ G). The detection rate in the gallium detectors turns out to be especially sensitive to the magnitude of $\\Delta m^2$. Predictions for forthcoming solar-neutrino experiments are made.

  10. A photomicrodynamic system with a mechanical resonator monolithically integrated with laser diodes on gallium arsenide.

    PubMed

    Ukita, H; Uenishi, Y; Tanaka, H

    1993-05-01

    A cantilever resonant microbeam, laser diodes, and a photodiode have been fabricated on the surface of a gallium arsenide substrate. The microbeam is excited photothermally by light from a laser diode. The vibration is detected with a photodiode as the variation in light output caused by the difference in optical length between the microbeam and another laser diode. A high carrier-to-noise ratio (45 decibels) is achieved with a short (3 micrometers) external cavity length. Such a small distance allows a lensless system, which increases the ease of fabrication. This work could lead to applications in which photomicrodynamic systems are monolithically integrated on a gallium arsenide substrate with surface micromachining technology. PMID:17746111

  11. Homoepitaxial n-core: p-shell gallium nitride nanowires: HVPE overgrowth on MBE nanowires.

    PubMed

    Sanders, Aric; Blanchard, Paul; Bertness, Kris; Brubaker, Matthew; Dodson, Christopher; Harvey, Todd; Herrero, Andrew; Rourke, Devin; Schlager, John; Sanford, Norman; Chiaramonti, Ann N; Davydov, Albert; Motayed, Abhishek; Tsvetkov, Denis

    2011-11-18

    We present the homoepitaxial growth of p-type, magnesium doped gallium nitride shells by use of halide vapor phase epitaxy (HVPE) on n-type gallium nitride nanowires grown by plasma-assisted molecular beam epitaxy (MBE). Scanning electron microscopy shows clear dopant contrast between the core and shell of the nanowire. The growth of magnesium doped nanowire shells shows little or no effect on the lattice parameters of the underlying nanowires, as measured by x-ray diffraction (XRD). Photoluminescence measurements of the nanowires show the appearance of sub-bandgap features in the blue and the ultraviolet, indicating the presence of acceptors. Finally, electrical measurements confirm the presence of electrically active holes in the nanowires. PMID:22025018

  12. Thermodynamic property evaluation and magnetic refrigeration cycle analysis for gadolinium gallium garnet

    SciTech Connect

    Murphy, R.W.

    1994-12-01

    Based on relevant material property data and previous model formulations, a magnetothermodynamic property map for gadolinium gallium garnet (Gd{sub 3}Ga{sub 5}O{sub 12}) was adapted for refrigeration cycle analysis in the temperature range 4-40 K and the magnetic field range 0-6 T. Employing methods similar to those previously developed for other materials and temperature ranges, assessments of limitations and relative performance were made for Carnot, ideal regenerative, and pseudo-constant field regenerative cycles. It was found that although Carnot cycle limitations on available temperature lift for gadolinium gallium garnet are not as severe as the limitations for materials previously examined, considerable improvement in cooling capacity and temperature lift combinations can be achieved by using regenerative cycles if serious loss mechanisms are avoided.

  13. Osteomyelitis and infarction in sickle cell hemoglobinopathies: differentiation by combined technetium and gallium scintigraphy

    SciTech Connect

    Amundsen, T.R.; Siegel, M.J.; Siegel, B.A.

    1984-12-01

    Clinical records and scintigrams were reviewed of 18 patients with sickle cell hemoglobinophaties who had undergone combined technetium and gallium scintigraphy during 22 separate episodes of suspected osseous infection. The combined scintigrams were correctly interpreted as indicating osteomyelitis in four studies. Of 18 studies in patients with infarction, the combined scintigrams were correctly interpreted in 16 and showed either no local accumulation of Ga-67 or less accumulation than that of Tc-99m MDP at symptomatic sites. In the other two studies, the scintigrams were falsely interpreted as indicating osteomyelitis and showed congruent, increased accumulation of both Tc-99, MDP and Ga-67. This pattern must be considered indeterminate. Overall, the results indicate that the combination of technetium and gallium scintigraphy is an effective means to distinguish osteomyelitis from infarction in patients with sickle cell hemoglobinopathies.

  14. Chronic osteomyelitis: bone and gallium scan patterns associated with active disease

    SciTech Connect

    Tumeh, S.S.; Aliabadi, P.; Weissman, B.N.; McNeil, B.J.

    1986-03-01

    Bone and gallium scans are used to assess osteomyelitis patients with prior bone disease. To refine the criteria for interpreting these scans, the data from 136 consecutive patients with clinically suspected osteomyelitis were reviewed. Active osteomyelitis was diagnosed with surgery or biopsy and culture in 49 patients, excluded with the same criteria in 16, and excluded by clinical follow-up for at least 6 months in 71. Five different scintigraphic patterns were found. The true-positive and false-positive ratios, the likelihood ratios, and posterior probabilities for active osteomyelitis in each pattern were calculated. Only one pattern (gallium uptake exceeding bone-seeking radiopharmaceutical uptake) was indicative of active disease. Other patterns slightly raised or decreased the probability of disease. The extent of these changes varies directly with the prior probability of disease, determined from patient-specific factors (e.g., clinical data, laboratory data, findings on plain films) known best by the referring clinician.

  15. Distinctive Signature of Indium Gallium Nitride Quantum Dot Lasing in Microdisks Cavities

    E-print Network

    Woolf, Alexander; Aharanovich, Igor; Zhu, Tongtong; Niu, Nan; Wang, Danqing; Oliver, Rachel A; Hu, Evelyn L

    2014-01-01

    Low threshold lasers realized within compact, high quality optical cavities enable a variety of nanophotonics applications. Gallium nitride (GaN) materials containing indium gallium nitride (InGaN) quantum dots and quantum wells offer an outstanding platform to study light matter interactions and realize practical devices such as efficient light emitting diodes and nanolasers. Despite progress in the growth and characterization of InGaN quantum dots, their advantages as the gain medium in low threshold lasers have not been clearly demonstrated. This work seeks to better understand the reasons for these limitations by focusing on the simpler, limited-mode microdisk cavities, and by carrying out comparisons of lasing dynamics in those cavities using varying gain media including InGaN quantum wells, fragmented quantum wells, and a combination of fragmented quantum wells with quantum dots. For each gain medium, we utilize the distinctive, high quality (Q~5500) modes of the cavities, and the change in the highest ...

  16. Copper-tantalum alloy

    DOEpatents

    Schmidt, Frederick A. (Ames, IA); Verhoeven, John D. (Ames, IA); Gibson, Edwin D. (Ames, IA)

    1986-07-15

    A tantalum-copper alloy can be made by preparing a consumable electrode consisting of an elongated copper billet containing at least two spaced apart tantalum rods extending longitudinally the length of the billet. The electrode is placed in a dc arc furnace and melted under conditions which co-melt the copper and tantalum to form the alloy.

  17. Ductile transplutonium metal alloys

    DOEpatents

    Conner, W.V.

    1981-10-09

    Alloys of Ce with transplutonium metals such as Am, Cm, Bk and Cf have properties making them highly suitable as souces of the transplutonium element, e.g., for use in radiation detector technology or as radiation sources. The alloys are ductile, homogeneous, easy to prepare and have a fairly high density.

  18. ZIRCONIUM ALLOYS FOR REACTORS

    Microsoft Academic Search

    Nishihara

    1960-01-01

    The general characteristics of the reactor-grade Zr alloys are revewed, ; including the physical properties of pure Zr and of the pertinent alloys, ; manufacturing processes of Zr sponge and of Zircaloy, electric arc welding ; methods for the pure metal and the ingot, hot and cold working, annealing and ; welding. The high temperatare behavior of Zircaloy, Ozhennite and

  19. Shape Memory Alloys

    Microsoft Academic Search

    Abhijit Bhattacharyya; Dimitris C Lagoudas

    2007-01-01

    This special issue on shape memory alloys (SMA) is an encore to a special issue on the same topic edited by us six years ago (Smart Mater. Struct.9 (5) October 2000). A total of 19 papers is offered in this issue, organized into the three broad categories of modeling, characterization and applications. In addition to thermally activated shape memory alloys,

  20. Rhenium alloys in electronics

    Microsoft Academic Search

    E. M. Savitskii; M. A. Tylkina; A. M. Levin

    1980-01-01

    The book presents information on the utilization of rhenium and its alloys in electronics for electronic vacuum devices such as preheaters, cathodes, and screens, and also in the thin-film microelectronic designs. Data on physical and chemical interaction of rhenium with other elements are generalized, and basic theoretical premises in the development of rhenium alloys with specified properties are summarized. The

  1. Cesium iodide alloys

    DOEpatents

    Kim, H.E.; Moorhead, A.J.

    1992-12-15

    A transparent, strong CsI alloy is described having additions of monovalent iodides. Although the preferred iodide is AgI, RbI and CuI additions also contribute to an improved polycrystalline CsI alloy with outstanding multispectral infrared transmittance properties. 6 figs.

  2. Ductile transplutonium metal alloys

    DOEpatents

    Conner, William V. (Boulder, CO)

    1983-01-01

    Alloys of Ce with transplutonium metals such as Am, Cm, Bk and Cf have properties making them highly suitable as sources of the transplutonium element, e.g., for use in radiation detector technology or as radiation sources. The alloys are ductile, homogeneous, easy to prepare and have a fairly high density.

  3. Mechanically alloyed, ferritic oxide dispersion strengthened alloys: structure and properties

    Microsoft Academic Search

    A. Czyrska-Filemonowicz; B. Dubiel

    1997-01-01

    The paper presents information concerning the production of oxide dispersion strengthened (ODS) alloys by mechanical alloying process. The macro- and microstructures of the ferritic ODS alloys, INCOLOY MA 956 and PM2000 are discussed in detail. The basic engineering properties of these alloys, namely oxidation resistance and mechanical properties, especially tensile, compression and high temperature creep, are outlined.

  4. Alloying aluminum alloys with scandium and zirconium additives

    Microsoft Academic Search

    V. G. Davydov; V. I. Elagin; V. V. Zakharov; D. Rostoval

    1996-01-01

    In recent years Russian specialists have developed industrial weldable aluminum alloys alloyed with a small amount of scandium. Scandium added to existing weldable aluminum alloys improves considerably the set of their operational properties. In addition, the presence of scandium makes it possible to create new materials superior to traditional aluminum alloys. The present paper is devoted to problems of simultaneous

  5. First-principles calculations for AlN, GaN, and InN: Bulk and alloy properties

    SciTech Connect

    Wright, A.F.; Nelson, J.S.

    1995-02-01

    First-principles density-functional calculations utilizing ab initio pseudopotentials and plane-wave expansions are used to determine lattice parameters, bulk moduli, and band structures for AlN, GaN and InN. It is found that large numbers of plane waves are necessary to resolve the nitrogen 2p wave functions and that explicit treatment of the gallium 3d and indium 4d electrons is important for an accurate description of GaN and InN. Several properties of ternary zinc-blende alloys are determined including their bond-length and bond-angle relaxation and their energy-gap bowing parameters. The similarity of the calculated zinc-blende and wurtzite direct gaps also allows estimates to be made of the energy gap versus composition for wurtzite alloys.

  6. Clinical relevance of gallium-67 scintigraphy in lymphoma before and after therapy

    Microsoft Academic Search

    Corinne Delcambre; Oumedaly Reman; Michel Henry-Amar; Anne-Marie Peny; Margaret Macro; Stéphane Cheze; Jean-Yves Génot; Alain Tanguy; Odile Switsers; Hoa Ly Van; Jean-Etienne Couëtte; Michel Leporrier; Stéphane Bardet

    2000-01-01

    .   The clinical impact of gallium-67 scintigraphy before and after therapy for lymphoma remains controversial. The aims of this\\u000a study were: (1) to compare the staging of lymphoma by 67Ga scintigraphy only with staging by clinical examination and conventional imaging (CI), and (2) to analyse the clinical relevance\\u000a of both 67Ga imaging and CI after treatment. From March 1995 to

  7. Radiation effects in silicon and gallium arsenide solar cells using isotropic and normally incident radiation

    Microsoft Academic Search

    B. E. Anspaugh; R. G. Downing

    1984-01-01

    Several types of silicon and gallium arsenide solar cells were irradiated with protons with energies between 50 keV and 10 MeV at both normal and isotropic incidence. Damage coefficients for maximum power relative to 10 MeV were derived for these cells for both cases of omni-directional and normal incidence. The damage coefficients for the silicon cells were found to be

  8. Low-energy ion assisted deposition of epitaxial gallium nitride films

    Microsoft Academic Search

    J. W. Gerlach; D. Schrupp; K. Volz; M. Zeitler; B. Rauschenbach; A. Anders

    1999-01-01

    Epitaxial gallium nitride thin films were grown on c-plane and r-plane sapphire by low-energy ion assisted deposition in high vacuum using a constricted glow discharge plasma source for the supply of nitrogen. Instead of preparing a conventional low-temperature buffer layer, a single-temperature process with initial growth rate ramp was performed. The crystallographic structure and texture, defect distribution, morphology and topography

  9. Msm Photodetectors for Two-Dimensional Meander Channel CCD Imagers on Gallium Arsenide

    Microsoft Academic Search

    Nercy Bozorgebrahimi

    1991-01-01

    This dissertation describes the design, fabrication, and performance of metal-semiconductor-metal (MSM) photodetectors on gallium arsenide (GaAs) and demonstrates their application in charge-coupled-device (CCD) imagers by integrating them with meander channel CCDs on GaAs in a two-dimensional imager device. The MSM photodetectors have a simple structure formed by interdigitated aluminum electrodes on a semi -insulating (SI) GaAs substrate. The CCD structure

  10. The optical and electrical effects of high concentrations of defects in irradiated crystalline gallium arsenide

    Microsoft Academic Search

    R. Coates; E. W. J. Mitchell

    1975-01-01

    The damage produced by fast neutron irradiation of gallium arsenide has been studied by a number of techniques. The electrical resistivity, which increases with dose at low doses to semi-insulating values, shows a remarkable, specimen-independent decrease for doses greater than 1017 n cm-2 from values of ca. 109 Omega cm to 3 Omega cm for the highest dose of 1.5

  11. Nanoscale self-assembly of high-efficiency copper indium gallium selenide photovoltaic thin films

    Microsoft Academic Search

    Louay Eldada

    2009-01-01

    We demonstrate photovoltaic integrated circuits (PVIC) with high-quality large-grain Copper Indium Gallium Selenide (CIGS) obtained with the unique combination of low-cost ink-based or Physical Vapor Deposition (PVD) based nanoengineered precursor thin films and a reactive transfer printing method. Reactive transfer is a two-stage process relying on chemical reaction between two separate precursor films to form CIGS, one deposited on the

  12. Spectroscopic Ellipsometry Characterization of Variable Cu Concentration in Copper Indium Gallium di-Selenide Photovoltaic Films

    Microsoft Academic Search

    J. C. Verley; T. E. Furtak

    2000-01-01

    Copper indium gallium di-selenide (CIGS) is among the most promising thin-film photovoltaic (PV) materials. Solar cells, using CIGS as an absorber layer, have achieved greater than 18 percent power conversion efficiencies on the laboratory scale. The best CIGS based photovoltaics have been created by utilizing the so-called three-stage process for the growth of the absorber layer. Standard substrates consist of

  13. Manufacture of large-area copper indium (gallium) diselenide thin films for photovoltaic applications

    Microsoft Academic Search

    Gregory M. Hanket

    1999-01-01

    Issues relevant to the commercial-scale manufacture of copper indium (gallium) diselenide (CIS\\/CIGS) thin films were examined. These include CIS\\/CIGS formation kinetics, the design of multiple-source, large-area thermal evaporation systems, and optical flux measurement. Selenizations of copper, indium, and Cu-In precursor films by thermal evaporation at 400°C were performed. The unique aspect of the deposition system was the ability to rapidly

  14. High-efficiency, Cd-free copper–indium–gallium–diselenide\\/polymer hybrid solar cells

    Microsoft Academic Search

    Vignesh Gowrishankar; Christine K. Luscombe; Michael D. McGehee; Jean M. J. Fréchet

    2007-01-01

    The use of a semiconducting polymer as a buffer layer replacement for CdS in traditionally all-inorganic copper–indium–gallium–diselenide (CIGS)-based solar cells is reported. The semiconducting polymer used is poly(benzimidazobenzophenanthroline) (BBL), which has physical and electronic properties that facilitate a suitable junction between the CIGS and the top electrode. We report on the fabrication, physical properties and photovoltaic characteristics of such Cd-free

  15. Copper–indium–gallium–diselenide\\/molybdenum layers analyzed by corrected SIMS depth profiles

    Microsoft Academic Search

    G. Bilger; P. O. Grabitz; A. Strohm

    2004-01-01

    Polycrystalline copper–indium–gallium–diselenide (CIGS) may act as absorber material for solar radiation in thin film solar cells. CIGS layers are grown on molybdenum back contacts deposited on glass or flexible substrates. During the preparation process, substrate elements diffuse across the back contact into CIGS. We investigate the diffusion into the CIGS\\/Mo layers by SIMS depth profiling corrected with respect to recoil

  16. Copper indium gallium diselenide thin films for sun angle detectors in space applications

    Microsoft Academic Search

    Tobias Böhnke; Marika Edoff

    2009-01-01

    This work reports on processing, analysis and characterization of copper indium gallium diselenide (CIGS) used as a photosensitive layer for sensors such as sun angle detectors in space applications. CIGS-based solar cell devices with different CIGS layer thicknesses and the pn-junction located on the opposite side of the incidence of light were illuminated through their ultra-thin transparent molybdenum back contacts.

  17. Precision determination of the K-shell fluorescence yield of gallium

    Microsoft Academic Search

    H. U. Freund; H. Genz; J. B. Siberts; R. W. Fink

    1969-01-01

    A large, wall-less multiwire proportional counter containing a gaseous source of 71GeH4 has been used in a precision determination of the K-shell fluorescence yield of gallium. Runs were performed with various pressures (0.3-6 atm) of pure propane and of argon-propane mixtures. Extensive evaluation was made of the detector efficiencies for K-Auger electrons and K X-rays following K-capture events in 71Ge.

  18. Analysis of electroluminescence spectra of silicon and gallium arsenide p-n junctions in avalanche breakdown

    Microsoft Academic Search

    M. Lahbabi; A. Ahaitoufa; M. Fliyou; E. Abarkan; J.-P. Charles; A. Bath; A. Hoffmann; Sherra E. Kerns; Kerns Jr. David V

    2004-01-01

    We present a generalized study of light emission from reverse biased p-n junctions under avalanche breakdown conditions. A model is developed based on direct and indirect interband processes including self-absorption to describe measured electroluminescence spectra. This model was used to analyze experimental data for silicon (Si) and gallium arsenide p-n junctions and can be extended to several types of semiconductors

  19. Annealing of radiation damaged gallium arsenide solar cells by laser illumination. Master`s thesis

    Microsoft Academic Search

    1994-01-01

    In this research, preliminary results of a new approach for annealing previously irradiated gallium arsenide solar cells is reported. This technique examines the use of laser illumination to induce Forward-Biased current annealing. Five GaAs solar cells were irradiated with 65 MeV electrons at varying fluence levels. Visible laser light produced a 0.5 A\\/sq cm forward-biased current density and raised the

  20. Annealing of radiation damaged gallium arsenide solar cells by laser illumination

    Microsoft Academic Search

    Richard D. Kramer

    1994-01-01

    In this research, preliminary results of a new approach for annealing previously irradiated Gallium Arsenide solar cells is reported. This technique examines the use of laser illumination to induce Forward-Biased current annealing. Five GaAs solar cells were irradiated with 65 MeV electrons at varying fluence levels. Visible laser light produced a 0.5 A\\/sq cm forward-biased current density and raised the

  1. BRIEF COMMUNICATIONS: Anisotropic diffraction of light in a gallium phosphide crystal with induced anisotropy

    NASA Astrophysics Data System (ADS)

    Azamatov, Z. T.; Voloshinov, V. B.; Mamatdzhanov, F. D.; Parygin, V. N.

    1981-09-01

    Experimental and theoretical studies were made of the anisotropy of the Bragg diffraction of light by ultrasound in gallium phosphide crystals. An external static pressure produced a controlled optical anisotropy in the initially isotropic GaP samples. In this way a birefringence of ~10-4 was induced and it corresponded to acoustic frequencies of hundreds of megahertz. This should make it possible to use effectively acoustooptic GaP crystals in anisotropic diffraction devices for the control of laser radiation.

  2. A mobility study of the radiation induced order effect in gallium arsenide

    Microsoft Academic Search

    Anouar Jorio; Martin Parenteau; Marcel Aubin; Cosmo Carlone; Shyam M. Khanna; John W. Gerdes Jr

    1994-01-01

    N-type gallium arsenide doped with silicon was irradiated with reactor neutrons to 1012, 3×1012, 1013 , 3×1013, 1014, 3×1014, 1015, and 3×1015 cm -2 (1 MeV equivalent fluence). The temperature dependence of the mobility was obtained after irradiation and annealing to 550°C for 30 minutes. The maximum value of the mobility, ?max, with respect to temperature was obtained as a

  3. Preliminary survey report: control technology for gallium arsenide processing at Texas Instruments, Dallas, Texas

    Microsoft Academic Search

    Lenihan

    1988-01-01

    A study was conducted at Texas Instruments, Dallas, Texas, to evaluate the technology currently available for controlling gallium arsenide (GaAs) dusts in the semiconductor industry. At the facility, GaAs optoelectronic devices were produced along with monolithic microwave integrated circuits and field effect transistors in low-volume quantities. Hazardous chemicals were used. Chemical fume hoods were used in the production areas with

  4. Ab initio study of the dielectric properties of silicon and gallium arsenide using polarized Wannier functions

    Microsoft Academic Search

    Pablo Fernández; Andrea dal Corso; Alfonso Baldereschi

    1998-01-01

    We present a first-principles calculation of the electronic properties of crystalline silicon and gallium arsenide in a uniform electric field. Polarized Wannier-like functions which are confined in a finite region are obtained by minimizing a total-energy functional which depends explicitly on the macroscopic polarization of the solid. The polarization charge density and the electronic dielectric constant are computed via finite

  5. Assembly and packaging of microwave gallium arsenide devices for the space environment

    NASA Astrophysics Data System (ADS)

    Wescott, C.

    1991-03-01

    Work carried out investigating the placement, wire bonding and packaging of gallium arsenide devices for space applications is described. Selection of adhesives for die placement and lid sealing and comparison with a gold/tin eutectic for the same process are described. An investigation of thermosonic gold wire wedge bonding is presented. Identification of a ceramic microwave package is performed. Stress testing intended to be carried out on specially selected test pieces is discussed.

  6. Removal and recovery of gallium ion from solution by insoluble amphoteric starches

    Microsoft Academic Search

    Wu-Chung Chan; Wuchung

    1993-01-01

    The removal and recovery of gallium ion (Ga[sup +3]) from a solution with the high cross-linked amphoteric starches containing the phosphate anionic group and the quaternary ammonium or tertiary amine cationic group was investigated. The adsorption capacity of tertiary amine phosphate starch (TAP) and quaternary ammonium phosphate starch (QAP) is 0.54 and 0.48 meq\\/g, respectively. The adsorption process has been

  7. Selective Separation of Gallium from Acidic Leach Solutions by Emulsion Liquid Membranes

    Microsoft Academic Search

    R. A. Kumbasar; O. Tutkun

    2006-01-01

    The separation and concentration of gallium from acidic leach solutions, containing various other ions such as iron, cobalt, nickel, zinc, cadmium, lead, copper, and aluminium, by an emulsion liquid membrane (ELM) technique using tributyl phosphate (TBP) as carrier has been presented. Liquid membrane consists of a diluent, a surfactant (ECA 4360J), and an extractant (TBP), and 0.1 M HCl or 0.1 M

  8. Molten gallium flux synthesis of known thermoelectric and novel magnetic inorganic clathrate compounds: Improving thermoelectric performance

    Microsoft Academic Search

    John Daniel Bryan

    2002-01-01

    Molten gallium metal has been used as a solvent to grow large single crystals of known inorganic thermoelectric clathrates Sr8Ga 16Ge30, Ba8Ga16Ge30, and Ba8Ga16Si30. X-ray diffraction, thermal analysis, electron microprobe, Glow Discharge Mass Spectrometry, temperature dependent electrical conductivity and Seebeck coefficient measurements characterized the single crystals. The Thermoelectric performance was shown to be heavily dependent on the synthetic conditions including

  9. An advanced space photovoltaic concentrator array using Fresnel lenses, gallium arsenide cells, and prismatic cell covers

    NASA Technical Reports Server (NTRS)

    O'Neill, Mark J.; Piszczor, Michael F.

    1988-01-01

    The current status of a space concentrator array which uses refractive optics, gallium arsenide cells, and prismatic cell covers to achieve excellent performance at a very low array mass is documented. The prismatically covered cells have established records for space cell performance (24.2 percent efficient at 100 AM0 suns and 25 C) and terrestrial single-junction cell performance (29.3 percent efficient at 200 AM1.5 suns and 25 C).

  10. Quartz homeotypic gallium-orthophosphate-a new high tech piezoelectric material

    Microsoft Academic Search

    P. W. Krempl

    1994-01-01

    In the recent years, the crystallographic and physical properties of quartz homeotypic gallium orthophosphate (GaPO4) have been studied and are summarized. Compared with quartz, these crystals show higher piezoelectric coefficients and therefore a larger electromechanical coupling. Its alpha-quartz-structure is stable up to 1206 K, where a transition to a cristobalite-like structure occurs. An alpha-beta transition does not occur, because the

  11. A thin film indium gallium arsenide focal plane array for visible and near infrared hyperspectral imaging

    Microsoft Academic Search

    Marshall J. Cohen; Michael J. Lange; Martin H. Ettenberg; Peter Dixon; G. H. Olsen

    1999-01-01

    Indium gallium arsenide (InGaAs) focal plane arrays (FPAs) have proven useful in a wide variety of scientific, commercial, and military applications ranging from near infrared spectroscopy to night vision imaging. In a two-dimensional InGaAs FPA, an InGaAs photodiode array is hybrid-integrated to a silicon CMOS readout integrated circuit using indium bump-bonding techniques. The array is backside-illuminated with a long wavelength

  12. Fabrication of optoelectronic microwave linear and ring resonators on a gallium arsenide substrate

    E-print Network

    Yeh, Chun-Liang

    1993-01-01

    for the degree of MASTER OF SCIENCE August 1993 Major Subject: Electrical Engineering FABRICATION OF OPTOELECTRONIC MICROWAVE LINEAR AND RING RESONATORS ON A GALLIUM ARSENIDE SUBSTRATE A Thesis by CHUN-LIANG YEH Approved as to style and content by: Mark... structure is selected as the basic configuration for the resonator based on its convenience to be fabricated by photolithographic processes and its ease of integration with other passive and active microwave devices. Using SMA 50' connectors, microstrip...

  13. Wide band gap Gallium Phosphide solar cells for multi-junction solar cell system

    Microsoft Academic Search

    Xuesong Lu; S. R. Huang; M. Diaz; R. L. Opila; A. Barnett

    2010-01-01

    Gallium Phosphide (GaP) solar cells have been designed, fabricated, characterized and analyzed as candidates for the top junction solar cell in a multi-junction solar cell system. Liquid phase epitaxy (LPE) has been used as the growth method for the epitaxial layers. Open circuit voltage (Voc) of 1.535V has been achieved under one sun illumination from the outdoor test. Quantum efficiency

  14. Paclitaxel plus gallium nitrate and filgrastim in patients with refractory malignancies: a phase I trial.

    PubMed

    Sandler, A; Fox, S; Meyers, T; Christou, A; Weber, G; Gonin, R; Loehrer, P J; Einhorn, L H; Dreicer, R

    1998-04-01

    To determine the maximally tolerated dose of paclitaxel with and without filgrastim (G-CSF) when administered as a 24-hour intravenous infusion after a 120-hour infusion of gallium nitrate at a fixed dose of 300 mg/m2/24 hours, 40 patients were entered onto a trial lasting from September 1994 to September 1996. Eligibility included a diagnosis of an advanced malignancy not amenable to curative therapy and up to one previous chemotherapy regimen for metastatic disease. Gallium was administered at a fixed dose of 300 mg/m2/day as a continuous intravenous infusion for 120 hours. Paclitaxel starting at 90 mg/m2 was given concurrently with the last 24 hours of the gallium as a 24-hour intravenous infusion. Cycles were repeated every 21 days. Once the maximum tolerated dose (MTD) of paclitaxel was reached, G-CSF (5 microg/kg/day days 7-16) was added and paclitaxel dose escalation continued. The MTD for paclitaxel without G-CSF was 110 mg/m2 and 225 mg/m2 with G-CSF, with neutropenia being the dose-limiting toxicity. A partial response was noted in a patient who had thymoma and a complete response was achieved in a patient who had colon cancer. The recommended phase II dosage is gallium nitrate at 300 mg/m2/day over 120 hours, with paclitaxel at 110 mg/m2 over 24 hours without G-CSF or 225 mg/m2 over 24 hours with G-CSF and 0.5 mg calcitriol on days 1 through 7. Further trials of this modified regimen for outpatient administration are in progress. PMID:9537208

  15. Theoretical calculations of the temperature dependence of the electrical and thermal conductivities of liquid gallium

    Microsoft Academic Search

    M. Sayem El-Daher; Richard D. Murphy

    2005-01-01

    The electrical and thermal resistivities of liquid gallium are calculated over a range of temperatures above the melting point\\u000a using the solutions of the Boltzmann equation. The experimental x-ray structure factor of Waseda and the form factor derived\\u000a using the Heine-Abarenkov model potential are used in these calculations. The ratio of the electrical and thermal conductivities\\u000a is calculated and compared

  16. Characteristics of trap-filled gallium arsenide photoconductive switches used in high gain pulsed power applications

    Microsoft Academic Search

    N. E. ISLAM; E. SCHAMILOGLU; ALAN MAR; GUILLERMO M. LOUBRIEL; FRED J. ZUTAVERN; R. P. JOSHI

    2000-01-01

    The electrical properties of semi-insulating (SI) Gallium Arsenide (GaAs) have been investigated for some time, particularly for its application as a substrate in microelectronics. Of late this material has found a variety of applications other than as an isolation region between devices, or the substrate of an active device. High resistivity SI GaAs is increasingly being used in charged particle

  17. Synthesis, characterization, growth mechanism, photoluminescence and field emission properties of novel dandelion-like gallium nitride

    Microsoft Academic Search

    Ghulam Nabi; Chuanbao Cao; Waheed S. Khan; Sajad Hussain; Zahid Usman; Muhammad Safdar; Sajjad Hussain Shah; Noor Abass Din Khattak

    2011-01-01

    Dandelion-like gallium nitride (GaN) microstructures were successfully synthesized via Ni catalyst assisted chemical vapor deposition method at 1200°C under NH3 atmosphere by pre-treating precursors with aqueous ammonia. The as-synthesized product was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). X-ray diffraction analysis revealed that as-synthesized dandelion-like GaN was pure and has hexagonal wurtzite

  18. Alloys for aerospace

    SciTech Connect

    Tuominen, S.; Wojcik, C. [Teledyne Wah Chang, Albany, OR (United States)

    1995-04-01

    Aerospace industries require special allows with many properties tailored to meet specific needs. Prerequisites include clean melting techniques to maintain low impurity levels, tight control of alloy chemistry, and the analytical capability to characterize the product. Teledyne Wah Chang (TWC) produces specially refractory metals, including zirconium, hafnium, titanium, niobium and vanadium, which are essential components of many aerospace alloys. Alloys are prepared by vacuum-arc-remelting (VAR) or electron beam (EB) melting, and ingots are processed to products ranging from bar and tube stock to wire and foil. Chemical, mechanical, and microstructural tests are all conducted at TWC`s in-house laboratory facilities. Of the alloys described here, Ti-3Al-2.5V, Tiadyne 3515 (Alloy C), NiTiFe, and C-103 are produced commercially, while orthorhombic titanium aluminides are promising candidates for future light-weight composite matrices.

  19. Alloys in energy development

    SciTech Connect

    Frost, B.R.T.

    1984-02-01

    The development of new and advanced energy systems often requires the tailoring of new alloys or alloy combinations to meet the novel and often stringent requirements of those systems. Longer life at higher temperatures and stresses in aggressive environments is the most common goal. Alloy theory helps in achieving this goal by suggesting uses of multiphase systems and intermediate phases, where solid solutions were traditionally used. However, the use of materials under non-equilibrium conditions is now quite common - as with rapidly solidified metals - and the application of alloy theory must be modified accordingly. Under certain conditions, as in a reactor core, the rate of approach to equilibrium will be modified; sometimes a quasi-equilibrium is established. Thus an alloy may exhibit enhanced general diffusion at the same time as precipitate particles are being dispersed and solute atoms are being carried to vacancy sinks. We are approaching an understanding of these processes and can begin to model these complex systems.

  20. In-situ TEM observation of aluminum embrittlement by liquid gallium

    SciTech Connect

    Hugo, R.C.; Hoagland, R.G. [Washington State Univ., Pullman, WA (United States). Dept. of Mechanical and Materials Engineering] [Washington State Univ., Pullman, WA (United States). Dept. of Mechanical and Materials Engineering

    1998-01-06

    Liquid metal embrittlement (LME) occurs when some solids contact certain liquid metals. Normally ductile materials will exhibit brittle fracture behavior because of interactions between the solid metal and adsorbed liquid atoms. The fracture characteristics of different solid-liquid metal couples vary greatly. A requirement is that the liquid wets the surface of a solid. Ductile materials fail over a period of time, by slow and often discontinuous crack growth. For embrittlement to occur, the liquid metal atoms must be adsorbed at the crack tip. If the crack extends beyond the adsorbed atoms, it may become blunted and arrest. Thus the time necessary for failure depends on the transport of liquid metal atoms to the crack tip. The aluminum-gallium system exhibits this type of time-dependent failure. Liquid gallium penetrates the grain boundaries so that failure occurs primarily by intergranular fracture at applied stress levels as low as zero, although transgranular cleavage is sometimes observed for applied stress intensities of 4--5 MPa-m{sup 1/2}. This penetration proceeds much faster than can be accounted for by grain boundary diffusion, and occurs in the absence of any applied stress. The driving force is generally considered to be the reduction in interfacial energy which results when a high energy grain boundary is replaced with two lower energy aluminum-gallium interfaces. This study reports the results of grain boundary penetration observed in-situ in the TEM.

  1. Investigation of spin transport and accumulation in aluminum gallium arsenide

    NASA Astrophysics Data System (ADS)

    Misuraca, Jennifer

    This dissertation describes spin injection, transport, and detection experiments from Fe electrodes into a bulk AlGaAs channel. This semiconducting alloy is one of a class of persistent photoconductors, chosen as the spin transport medium because its carrier density can be tuned in a controlled manner via photoexcitation through the metal to insulator transition (MIT) in situ. This allows one to determine the dependence of spin lifetime on a variety of external parameters including carrier density, all on one sample. This research represents the first electrical spin-dependent measurements in this material and describes the dependence of the Hanle signal size and spin lifetime on bias, temperature, and carrier density. The photoexcitation needed to change the carrier density in this material comes from an infrared light-emitting diode (IR LED). The first step of this project was to characterize the new, highly Si doped Al0.3Ga 0.7As heterostructures, in order to determine how the illumination of the sample will affect the parameters of the material. To complete this study, Hall crosses were fabricated from the AlGaAs material and the transport properties were measured between 350 mK and 165 K. The resistivity, carrier density, and mobility were determined as a function of temperature for a variety of different illumination times. From this data, the MIT, scattering mechanisms, and the shape of the band tail of the density of states (DOS) were investigated. In fact, this is the first work to electrically probe the DOS in AlGaAs. Once the materials were characterized, they were used to fabricate lateral spin transport devices. Spin transport and accumulation were studied in detail via Hanle effect measurements, which measure the dephasing of electron spins in a perpendicular magnetic field. From these measurements, the spin lifetime of the material can be calculated, and is in the nanosecond range for all measured carrier densities. The spin lifetimes are measured using three distinct measurement configurations which all give consistent results. The dependence of spin lifetime and Hanle signal size are reported as a function of bias, temperature, and carrier density. This is the first spin transport experiment using a persistently photoconductive material as the spin transport channel in order to change the carrier density of the material in situ. The research in this dissertation successfully provides a framework for the continuation of spin injection and detection studies in this and other alloy semiconductors, and provides insight into how the spin lifetime depends on the doping levels in semiconductors.

  2. Ohmic contacts to N-type gallium nitride based semiconductors

    NASA Astrophysics Data System (ADS)

    Selvanathan, Deepak

    GaN-based field effect transistors are of importance in the area of microwave, high-power, and high-temperature applications. The AlGaN/GaN system is well suited for these applications due to their high electron drift velocities, high breakdown fields, and relatively good thermal conductivities. The chemical stability and mechanical hardness of the nitrides also afford these devices the latitude of operating in harsh environments. The direct energy gap of III-nitrides and their alloys also make them ideal candidates for opto-electronic devices, especially for emitters and detectors working in the green to deep-UV region of the electromagnetic spectrum. In this work, the development and characterization of electrical and materials performance of ohmic contacts are presented. Surface treatment techniques were developed to improve the electrical characteristics of ohmic contacts. Ti/Al/Mo/Au metallization scheme was developed to form ohmic contacts to n-GaN, n-AlxGa1-xN, and AlGaN/GaN HEMTs. Materials microstructural analysis techniques were used to understand the evolution of electrical behavior of these contacts at higher temperatures.

  3. MD study of the finite temperature effects on the phase ordering, stacking fault energy, and edge dislocation core structure in elemental Pu and Pu-Ga alloys

    NASA Astrophysics Data System (ADS)

    Karavaev, A. V.; Dremov, V. V.

    2015-02-01

    The Modified Embedded Atom Model (MEAM) of elemental plutonium and plutonium-gallium alloys has been tested for its ability to reproduce the correct ordering of the hcp and fcc phases that is crucial from the point of view of molecular dynamics simulation of elastic-plastic phenomena in the material. Stacking fault energy obtained with the MEAM is in agreement with experimental data. Results of the edge dislocation modeling at the ambient conditions evidence for rather wide dislocation core, namely, 5-6 Burgers vectors. The results of the MD simulation have been compared with those obtained early with recently developed Multi State-MEAM potential.

  4. Organo-gallium/indium chalcogenide complexes of copper(I): molecular structures and thermal decomposition to ternary semiconductors.

    PubMed

    Kluge, Oliver; Biedermann, Ralf; Holldorf, Joscha; Krautscheid, Harald

    2014-01-27

    Several organo-gallium/indium chalcogenide complexes of copper(I), stabilized by trialkylphosphines, were isolated, structurally characterized by using single-crystal X-ray diffraction, and investigated in thermolysis experiments. The syntheses with [E(Me3Si)2] (E=S, Se) as a starting material and a chalcogen source involve the elimination of volatile silyl acetate, silyl ethers, and methane from copper(I) acetate, and Group 13 metal trimethyl compounds, respectively. Chalcogenide complexes, according to the general formulas [(R3PCu)4(MeM)4E6] (1-6) and [(R3PCu)6(MeM)4M4S13] (7-9; with R=alkyl and M=Ga, In), and mixed chalcogenide-phenylchalcogenolate complexes [(iPr3PCuEPh)3(MeGaE)4] (10, 11) were isolated. The heavy atom cores of 1-6 consist of an octahedron of chalcogen atoms, interpenetrated by a cube of metal atoms. Depending on the steric demand of the phosphine ligands, two constitutions are observed; the metal atoms of the same element either forming tetrahedra, or parallelograms, respectively. This constitutional isomerism is further investigated by quantum chemical calculations. Complexes 7-9 contain a central sulfur atom, surrounded by two interpenetrating tetrahedra of Group 13 metal atoms, an octahedron of copper atoms, and an icosahedron of twelve outer sulfur atoms; the heavy atom framework of 10 and 11 is a "cut-out" of this structure. Thermolysis experiments include thermogravimetry measurements and subsequent Rietveld phase analysis of the residues by using powder X-ray diffraction. The homologous compounds 1, 3, 4, and 6 yield the respective crystalline ternary semiconductor material CuME2 at temperatures below 300?°C. Partial release of Me3 M during the thermolysis process results in excess copper in the residue and therefore in small amounts of additional binary copper chalcogenide phases or metallic CuM alloys. Compound 8 produces nanocrystalline CuGaS2 at about 300?°C. PMID:24338681

  5. Solvent extraction of gallium with non-ionic surfactants from hydrochloric acid solution and its application to metal recovery from zinc refinery residues

    Microsoft Academic Search

    T Kinoshita; S Akita; S Nii; F Kawaizumi; K Takahashi

    2004-01-01

    Studies have been conducted on the solvent extraction of gallium from hydrochloric acid media with three chlorinated organic solvents containing a non-ionic surfactant, polyoxyethylene nonyl phenyl ether (PONPE), as an extractant. The extraction of gallium(III) improved with an increase in HCl concentration, while that of other heavy metals except iron was suppressed in the whole acid range studied, resulting in

  6. The influence of random indium alloy fluctuations in indium gallium nitride quantum wells on the device behavior

    NASA Astrophysics Data System (ADS)

    Yang, Tsung-Jui; Shivaraman, Ravi; Speck, James S.; Wu, Yuh-Renn

    2014-09-01

    In this paper, we describe the influence of the intrinsic indium fluctuation in the InGaN quantum wells on the carrier transport, efficiency droop, and emission spectrum in GaN-based light emitting diodes (LEDs). Both real and randomly generated indium fluctuations were used in 3D simulations and compared to quantum wells with a uniform indium distribution. We found that without further hypothesis the simulations of electrical and optical properties in LEDs such as carrier transport, radiative and Auger recombination, and efficiency droop are greatly improved by considering natural nanoscale indium fluctuations.

  7. The influence of random indium alloy fluctuations in indium gallium nitride quantum wells on the device behavior

    SciTech Connect

    Yang, Tsung-Jui; Wu, Yuh-Renn, E-mail: yrwu@ntu.edu.tw [Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan (China); Shivaraman, Ravi; Speck, James S. [Department of Materials, University of California, Santa Barbara, California 93106 (United States)

    2014-09-21

    In this paper, we describe the influence of the intrinsic indium fluctuation in the InGaN quantum wells on the carrier transport, efficiency droop, and emission spectrum in GaN-based light emitting diodes (LEDs). Both real and randomly generated indium fluctuations were used in 3D simulations and compared to quantum wells with a uniform indium distribution. We found that without further hypothesis the simulations of electrical and optical properties in LEDs such as carrier transport, radiative and Auger recombination, and efficiency droop are greatly improved by considering natural nanoscale indium fluctuations.

  8. Stabilization of cubic lithium-stuffed garnets of the type “Li7La3Zr2O12” by addition of gallium

    NASA Astrophysics Data System (ADS)

    El Shinawi, Hany; Janek, Jürgen

    2013-03-01

    Cubic lithium-stuffed garnets of the type Li7La3Zr2O12 have been successfully stabilized by incorporation of gallium. The materials have been prepared by a sol-gel procedure with final calcination at 1085 °C for 6 h. Under the applied synthesis conditions, 0.3 mole of gallium ions (per mole of Li7La3Zr2O12) were sufficient to fully stabilize the cubic garnet-type phase. Increasing the fraction of gallium led to significant improvement of sinterability and lithium ion conductivity. Excess gallium ions, in the form of LiGaO2, act as a sintering aid and reside exclusively at the grain boundaries. The gallium-modified garnets showed conductivities up to 5.4 × 10-4 S cm-1 at 20 °C, and activation energies in the range 0.32-0.37 eV.

  9. Subtyping in alloy

    E-print Network

    Torlak, Emina, 1979-

    2004-01-01

    A type system for the Alloy modelling language is described that supports subtypes and allows overloading of relation names. No special syntactic features needed to be added to the language to support the type system; there ...

  10. Brazing dissimilar aluminum alloys

    NASA Technical Reports Server (NTRS)

    Dalalian, H.

    1979-01-01

    Dip-brazing process joins aluminum castings to aluminum sheet made from different aluminum alloy. Process includes careful cleaning, surface preparation, and temperature control. It causes minimum distortion of parts.

  11. High temperature niobium alloys

    Microsoft Academic Search

    J. J. Stephens; I. Ahmad

    1991-01-01

    This book covers the following areas regarding high temperature niobium alloys: atomic mass transport of interstitial solutes in niobium; electroplastic effect; dispersion strengthening; dispersion hardening by carbides; tensile behavior of tungsten\\/niobium composites; phase stability; mechanical properties; oxidation.

  12. Ductile ordered intermetallic alloys.

    PubMed

    Liu, C T; Stiegler, J O

    1984-11-01

    Many ordered intermetallic alloys have attractive high-temperature properties; however, low ductility and brittle fracture limit their use for structural applications. The embrittlement in these alloys is mainly caused by an insufficient number of slip systems (bulk brittleness) and poor grain-boundary cohesion. Recent studies have shown that the ductility and fabricability of ordered intermetallics can be substantially improved by alloying processes and control of microstructural features through rapid solidification and thermomechanical treatments. These results demonstrate that the brittleness problem associated with ordered intermetallics can be overcome by using physical metallurgical principles. Application of these principles will be illustrated by results on Ni(3)Al and Ni(3)V-Co(3)V-Fe(3)V. The potential for developing these alloys as a new class of high-temperature structural materials is discussed. PMID:17774926

  13. Mechanical alloying and milling

    Microsoft Academic Search

    C. Suryanarayana

    2001-01-01

    Mechanical alloying (MA) is a solid-state powder processng technique involving repeated welding, fracturing, and rewelding of powder particles in a high-energy ball mill. Originally developed to produce oxide-dispersion strengthened (ODS) nickel- and iron-base superalloys for applications in the aerospace industry, MA has now been shown to be capable of synthesizing a variety of equilibrium and non-equilibrium alloy phases starting from

  14. Thixoforming 7075 aluminium alloys

    Microsoft Academic Search

    S. Chayong; H. V. Atkinson; P. Kapranos

    2005-01-01

    Commercially extruded 7075 alloy (extrusion ratio of 16:1) has been used as a feedstock for thixoforming in order to investigate thixoformability of a high performance aluminium alloy. The microstructure in the semi-solid state consists of fine spheroidal solid grains surrounded by liquid. The results of thixoforming with one step, two-step and three-step induction heating regimes are presented. Typical defects in

  15. Effect of barrier height on friction behavior of the semiconductors silicon and gallium arsenide in contact with pure metals

    NASA Technical Reports Server (NTRS)

    Mishina, H.; Buckley, D. H.

    1984-01-01

    Friction experiments were conducted for the semiconductors silicon and gallium arsenide in contact with pure metals. Polycrystalline titanium, tantalum, nickel, palladium, and platinum were made to contact a single crystal silicon (111) surface. Indium, nickel, copper, and silver were made to contact a single crystal gallium arsenide (100) surface. Sliding was conducted both in room air and in a vacuum of 10 to the minus 9th power torr. The friction of semiconductors in contact with metals depended on a Schottky barrier height formed at the metal semiconductor interface. Metals with a higher barrier height on semiconductors gave lower friction. The effect of the barrier height on friction behavior for argon sputtered cleaned surfaces in vacuum was more specific than that for the surfaces containing films in room air. With a silicon surface sliding on titanium, many silicon particles back transferred. In contrast, a large quantity of indium transferred to the gallium arsenide surface.

  16. Micromilling of Metal Alloys with Focused Ion Beam-Fabricated Tools

    SciTech Connect

    ADAMS,DAVID P.; VASILE,M.J.; BENAVIDES,GILBERT L.; CAMPBELL,ANN N.

    1999-11-05

    This work combines focused ion beam sputtering and ultra-precision machining as a first step in fabricating microstructure in metals and alloys. Specifically, {approx}25{micro}m diameter micro-end mills are made from cobalt M42 high-speed steel and C2 micrograin tungsten carbide tool blanks by ion beam sputtering. A 20 keV focused gallium beam defines tool cutting edges having radii of curvature < 0.1{micro}m. Micro-end mills having 2, 4 and 5 cutting edges successfully machine small trenches in 6061-T4 aluminum, brass, 4340 steel and polymethyl methacrylate. Machined trench widths are approximately equal to the tool diameters and surface roughnesses (rms) are {approx}150 nm or less. Microtools are robust and operate for more than 6 hours without fracture. Results from ultra-precision machining aluminum at feed rates as high as 50 mm/minute are included.

  17. Lead-gallium glasses and glass-ceramics doped with SiO2 for near infrared transmittance

    NASA Astrophysics Data System (ADS)

    Marczewska, Agnieszka; ?roda, Marcin; Nocu?, Marek; Sulikowski, Bogdan

    2015-07-01

    Lead-gallium glasses, due to the absence of typical glass-forming components, are characterized by an increased tendency to crystallization. Despite this, they are interesting materials due to a shift of IR absorption edge up to 6-7 ?m. The paper considers how the SiO2 dopant affects thermal stability and the UV-VIS and IR transmittance of lead-gallium glasses. The base lead-gallium glass (0.75PbO·0.25Ga2O3) was modified by the addition of 5, 10 and 15 mol% SiO2, respectively. DTA/DSC data showed that the glasses are characterized by the multi-stage crystallization, which is changed with the amount of silica doped. The XRD analysis confirmed that: (i) different forms of lead oxide crystallize after heat treatment of the glass, and (ii) the Ga2PbO4 phase is formed at higher temperatures. The silica admixture allowed inserting a few percent of BaF2 into the lead-gallium glass structure. It was found that a transparent glass-ceramic based on the lead-gallium glass with a low phonon barium fluoride phase can be obtained during the thermal treatment. The study of UV-VIS-IR transmittance shows that 10-15 mol% SiO2 in the lead-gallium glasses diminishes the absorption band in the range of 2.6-4 ?m due to the presence of hydroxyl groups and simultaneously reduces transmittance in the range of 5-6.5 ?m from 10 to 20%. Introduction of SiO2 to the glass results in the increase of transmittance in the shorter wavelength region and the UV-edge shift is observed. It was also confirmed that the BaF2 nanocrystallites exert no effect on the transmittance of the spectrum analyzed.

  18. Strength and fracture of uranium, plutonium and several their alloys under shock wave loading

    NASA Astrophysics Data System (ADS)

    Golubev, V. K.

    2012-08-01

    Results on studying the spall fracture of uranium, plutonium and several their alloys under shock wave loading are presented in the paper. The problems of influence of initial temperature in a range of - 196 - 800?C and loading time on the spall strength and failure character of uranium and two its alloys with molybdenum and both molybdenum and zirconium were studied. The results for plutonium and its alloy with gallium were obtained at a normal temperature and in a temperature range of 40-315?C, respectively. The majority of tests were conducted with the samples in the form of disks 4 mm in thickness. They were loaded by the impact of aluminum plates 4 mm thick through a copper screen 12 mm thick serving as the cover or bottom part of a special container. The character of spall failure of materials and the damage degree of samples were observed on the longitudinal metallographic sections of recovered samples. For a concrete test temperature, the impact velocity was sequentially changed and therefore the loading conditions corresponding to the consecutive transition from microdamage nucleation up to complete macroscopic spall fracture were determined. The conditions of shock wave loading were calculated using an elastic-plastic computer program. The comparison of obtained results with the data of other researchers on the spall fracture of examined materials was conducted.

  19. EXAMINATION AND PROPERTIES OF URANIUM ALLOYS

    Microsoft Academic Search

    H. A. Saller; F. A. Rough

    1953-01-01

    The heat treatment, microstructure, hardness, and density data for a ; series of uranium alloys are described. These are alloys which were studied ; because of their potential interest for high-temperature water-corrosion ; resistance. The alloys studied include uranium--zirconium biiiary alloys, ; uranium-- zirconium-base ternary alloys, and uranium --molybdenum alloys. ; (auth);

  20. Outer-sphere interaction of aluminum and gallium solvates with competitive anions in 1,2-propanediol solutions

    SciTech Connect

    Petrosyants, S.P.; Buslaeva, E.R.

    1986-04-01

    The interaction of aluminum and gallium solvates with ..pi..-acid ligand in 1,2-propanediol solutions has been investigated. The formation of associates of hexacoordinate aluminum solvates depends on the solvation of the anions in the bulk of the solution or on the faces of the solvento complexes. In the case of gallium the association of the solvates with the anions is determined by two factors: the existence of a configurational equilibrium for the solvento complexes and the preferential solvation of the competitive ..pi..-acid ligands.

  1. Optical and structural studies of compositional inhomogeneity in strain-relaxed indium gallium nitride films

    Microsoft Academic Search

    L. H. Robins; J. T. Armstrong; R. B. Marinenko; M. D. Vaudin; C. E. Bouldin; J. C. Woicik; A. J. Paul; W. R. Thurber; K. E. Miyano; C. A. Parker; J. C. Roberts; S. M. Bedair; E. L. Piner; M. J. Reed; N. A. El-Masry; S. M. Donovan; S. J. Pearton

    2000-01-01

    The structural and optical properties of indium gallium nitride (InxGa1-xN) films with 0.04

  2. Resonant second harmonic generation in a gallium nitride two-dimensional photonic crystal on silicon

    NASA Astrophysics Data System (ADS)

    Zeng, Y.; Roland, I.; Checoury, X.; Han, Z.; El Kurdi, M.; Sauvage, S.; Gayral, B.; Brimont, C.; Guillet, T.; Mexis, M.; Semond, F.; Boucaud, P.

    2015-02-01

    We demonstrate second harmonic generation in a gallium nitride photonic crystal cavity embedded in a two-dimensional free-standing photonic crystal platform on silicon. The photonic crystal nanocavity is optically pumped with a continuous-wave laser at telecom wavelengths in the transparency window of the nitride material. The harmonic generation is evidenced by the spectral range of the emitted signal, the quadratic power dependence vs. input power, and the spectral dependence of second harmonic signal. The harmonic emission pattern is correlated to the harmonic polarization generated by the second-order nonlinear susceptibilities ?zxx (2 ), ?zyy (2 ) and the electric fields of the fundamental cavity mode.

  3. Analytical and experimental procedures for determining propagation characteristics of millimeter-wave gallium arsenide microstrip lines

    NASA Technical Reports Server (NTRS)

    Romanofsky, Robert R.

    1989-01-01

    In this report, a thorough analytical procedure is developed for evaluating the frequency-dependent loss characteristics and effective permittivity of microstrip lines. The technique is based on the measured reflection coefficient of microstrip resonator pairs. Experimental data, including quality factor Q, effective relative permittivity, and fringing for 50-omega lines on gallium arsenide (GaAs) from 26.5 to 40.0 GHz are presented. The effects of an imperfect open circuit, coupling losses, and loading of the resonant frequency are considered. A cosine-tapered ridge-guide text fixture is described. It was found to be well suited to the device characterization.

  4. Use of gallium-67 liver imaging for the early diagnosis of Budd-Chiari syndrome

    SciTech Connect

    Garty, I.; Horovitz, I.; Keynan, A.

    1984-03-01

    A gallium-67 study, performed in a rare case of Budd-Chiari syndrome (BCS) in a 6-yr-old child, showed marked concentration of the tracer in the left and caudate lobes of the liver. Ten days later, a less specific and clear-cut appearance of left- and caudate-lobe concentration of Tc-99m phytate was obtained. The possible use of Ga-67 citrate imaging to diagnose BCS in its earliest stage is suggested, although no firm conclusion can be made from this single case.

  5. Europium doped gallium oxide nanostructures for room temperature luminescent photonic devices

    NASA Astrophysics Data System (ADS)

    Nogales, E; Méndez, B; Piqueras, J; García, J A

    2009-03-01

    Cathodoluminescence and photoluminescence techniques have been used to investigate room temperature light emission from ?-Ga2O3:Eu nanostructures, which were obtained by two methods. In one of them, a mixture of Ga2O3/Eu2O3 powders was used as precursor material and annealed under an argon flow. In the other one, undoped ?-Ga2O3 nanostructures were first obtained by thermal oxidation of metallic gallium and europium was subsequently incorporated by a diffusion process. Room temperature luminescence at 610 nm due to Eu3+ intraionic transitions from ?-Ga2O3:Eu has been observed. Waveguiding of this red emitted light through the structures was shown.

  6. Fabrication and characterization of cerium-doped terbium gallium garnet with high magneto-optical properties.

    PubMed

    Chen, Zhe; Hang, Yin; Yang, Lei; Wang, Jun; Wang, Xiangyong; Hong, Jiaqi; Zhang, Peixiong; Shi, Chunjun; Wang, Yaqi

    2015-03-01

    High optical quality (Tb((1-x))Ce(x))?Ga?O?? (TCGG) single crystal has been grown by the Czochralski method. The optical and magneto-optical properties of the TCGG are analyzed in detail and the Verdet constant (V) of TCGG is compared with that of undoped terbium gallium garnet (TGG) crystal. TCGG presents a very high transmittance, particularly in the visible-near infrared (VIS-NIR) region, and its V is obviously larger than that of TGG in the VIS-NIR region. The figure of merit and optical features point out the superior characteristics of TCGG with respect to TGG. PMID:25723441

  7. Optical properties and Faraday effect of ceramic terbium gallium garnet for a room temperature Faraday rotator.

    PubMed

    Yoshida, Hidetsugu; Tsubakimoto, Koji; Fujimoto, Yasushi; Mikami, Katsuhiro; Fujita, Hisanori; Miyanaga, Noriaki; Nozawa, Hoshiteru; Yagi, Hideki; Yanagitani, Takagimi; Nagata, Yutaka; Kinoshita, Hiroo

    2011-08-01

    The optical properties, Faraday effect and Verdet constant of ceramic terbium gallium garnet (TGG) have been measured at 1064 nm, and were found to be similar to those of single crystal TGG at room temperature. Observed optical characteristics, laser induced bulk-damage threshold and optical scattering properties of ceramic TGG were compared with those of single crystal TGG. Ceramic TGG is a promising Faraday material for high-average-power YAG lasers, Yb fiber lasers and high-peak power glass lasers for inertial fusion energy drivers. PMID:21934880

  8. Gallium scintigraphy in bronchogenic carcinoma. The effect of tumor location on sensitivity and specificity

    SciTech Connect

    Waxman, A.D.; Julien, P.J.; Brachman, M.B.; Tanasescu, D.E.; Ramanna, L.; Birnbaum, F.; Berman, D.S.; Koerner, S.K.

    1984-08-01

    Fifty-one patients with primary lung cancer were evaluated using /sup 62/Ga citrate scintigraphy with respect to detection of peripheral primary, hilar metastasis, and mediastinal metastasis. The results demonstrated the necessity for an understanding of the criteria used in considering the gallium scintigram as either positive or negative, as well as the instrumentation employed in performing the test before any meaningful sensitivity and specificity figures can be derived within a given institution. Only with this understanding can actual strategy for instituting invasive procedures be achieved.

  9. Near-infrared gallium nitride two-dimensional photonic crystal platform on silicon

    SciTech Connect

    Roland, I.; Zeng, Y.; Han, Z.; Checoury, X.; Blin, C.; El Kurdi, M.; Ghrib, A.; Sauvage, S.; Boucaud, P., E-mail: philippe.boucaud@ief.u-psud.fr [Institut d'Electronique Fondamentale, CNRS - Univ. Paris Sud 11, Bâtiment 220, F-91405 Orsay (France); Gayral, B. [Univ. Grenoble Alpes, INAC-SP2M, CEA-CNRS group “Nanophysique et Semiconducteurs,” F-38000 Grenoble (France); CEA, INAC-SP2M, CEA-CNRS group “Nanophysique et Semiconducteurs,” F-38000 Grenoble (France); Brimont, C.; Guillet, T. [Université Montpellier 2, Laboratoire Charles Coulomb UMR 5221, F-34905 Montpellier (France); Semond, F. [CRHEA-CNRS, Rue Bernard Grégory, F-06560 Valbonne (France)

    2014-07-07

    We demonstrate a two-dimensional free-standing gallium nitride photonic crystal platform operating around 1550?nm and fabricated on a silicon substrate. Width-modulated waveguide cavities are integrated and exhibit loaded quality factors up to 34?000 at 1575?nm. We show the resonance tunability by varying the ratio of air hole radius to periodicity, and cavity hole displacement. We deduce a ?7.9?dB/cm linear absorption loss for the suspended nitride structure from the power dependence of the cavity in-plane transmission.

  10. Optical properties and Faraday effect of ceramic terbium gallium garnet for a room temperature Faraday rotator

    NASA Astrophysics Data System (ADS)

    Yoshida, Hidetsugu; Tsubakimoto, Koji; Fujimoto, Yasushi; Mikami, Katsuhiro; Fujita, Hisanori; Miyanaga, Noriaki; Nozawa, Hoshiteru; Yagi, Hideki; Yanagitani, Takagimi; Nagata, Yutaka; Kinoshita, Hiroo

    2011-08-01

    The optical properties, Faraday effect and Verdet constant of ceramic terbium gallium garnet (TGG) have been measured at 1064 nm, and were found to be similar to those of single crystal TGG at room temperature. Observed optical characteristics, laser induced bulk-damage threshold and optical scattering properties of ceramic TGG were compared with those of single crystal TGG. Ceramic TGG is a promising Faraday material for high-average-power YAG lasers, Yb fiber lasers and high-peak power glass lasers for inertial fusion energy drivers.

  11. Ultrafast inverse Faraday effect in a paramagnetic terbium gallium garnet crystal

    NASA Astrophysics Data System (ADS)

    Mikhaylovskiy, R. V.; Hendry, E.; Kruglyak, V. V.

    2012-09-01

    Conventional wisdom dictates that magneto-optical and optomagnetic phenomena are reciprocal and of equal strength. We test this assumption in a pump-probe experimental study of the ultrafast inverse Faraday effect in a terbium gallium garnet crystal. The thorough quantitative analysis of the observed polarization response unambiguously demonstrates a remarkable discrepancy of several orders of magnitude between the strengths of the direct and the inverse effects. This finding further questions the validity of standard magnetic models relying on the use of the static Verdet constant on subpicosecond time scales.

  12. A Generator-Produced Gallium-68 Radiopharmaceutical for PET Imaging of Myocardial Perfusion

    PubMed Central

    Sharma, Vijay; Sivapackiam, Jothilingam; Harpstrite, Scott E.; Prior, Julie L.; Gu, Hannah; Rath, Nigam P.; Piwnica-Worms, David

    2014-01-01

    Lipophilic cationic technetium-99m-complexes are widely used for myocardial perfusion imaging (MPI). However, inherent uncertainties in the supply chain of molybdenum-99, the parent isotope required for manufacturing 99Mo/99mTc generators, intensifies the need for discovery of novel MPI agents incorporating alternative radionuclides. Recently, germanium/gallium (Ge/Ga) generators capable of producing high quality 68Ga, an isotope with excellent emission characteristics for clinical PET imaging, have emerged. Herein, we report a novel 68Ga-complex identified through mechanism-based cell screening that holds promise as a generator-produced radiopharmaceutical for PET MPI. PMID:25353349

  13. Isolated muscular sarcoidosis causing fever of unknown origin: The value of gallium-67 imaging

    SciTech Connect

    Patel, N.; Krasnow, A.; Sebastian, J.L.; Collier, B.D.; Hellman, R.S.; Isitman, A.T. (Medical College of Wisconsin, Milwaukee (USA))

    1991-02-01

    An unusual case of a patient with a long-standing fever of unknown origin (FUO) is presented whose gallium-67 ({sup 67}Ga) images revealed increased activity only in the calf muscles bilaterally. Other imaging modalities also failed to show chest or other abnormal findings. Subsequent biopsy of the right gastrocnemius muscle revealed noncaseating granulomas consistent with the diagnosis of sarcoidosis. When using {sup 67}Ga to evaluate a patient with a FUO, imaging of the extremities should always be included. Also, when abnormal Ga-67 uptake is present in the extremities, sarcoidosis should be included in the differential diagnosis.

  14. Development of gallium arsenide high-speed, low-power serial parallel interface modules: Executive summary

    NASA Technical Reports Server (NTRS)

    1988-01-01

    Final report to NASA LeRC on the development of gallium arsenide (GaAS) high-speed, low power serial/parallel interface modules. The report discusses the development and test of a family of 16, 32 and 64 bit parallel to serial and serial to parallel integrated circuits using a self aligned gate MESFET technology developed at the Honeywell Sensors and Signal Processing Laboratory. Lab testing demonstrated 1.3 GHz clock rates at a power of 300 mW. This work was accomplished under contract number NAS3-24676.

  15. Gallium citrate Ga 67 scintigraphic detection of chronic osteomyelitis in children with leukemia

    SciTech Connect

    Miller, J.H.; Ettinger, L.J.

    1986-03-01

    Chronic osteomyelitis producing unexplained fevers without localizing symptomatology may present difficulty in detection and differentiation in patients with leukemia. Gallium citrate Ga 67 scintigraphy offers a method of detection and localization of both the osseous and extraosseous manifestations of such a process. Once identified, further evaluation by conventional radiographic or sectional imaging techniques may further define the process. We describe three patients with leukemia and unexplained fever in whom occult chronic osteomyelitis was diagnosed by 67Ga scintigraphy, which offers an ideal screening procedure and should be utilized in this clinical setting.

  16. Quenching Alloys in Containerless Processing

    NASA Technical Reports Server (NTRS)

    Oran, W. A.

    1984-01-01

    Magnetic levitation and gas quenching combined in proposed method to melt and rapidly solidify alloys without contacting container walls. Method used to develop new carbides for drill bits, high-ductility structured steel and new high-strength superplastic alloys.

  17. Finding the Alloy Genome

    NASA Astrophysics Data System (ADS)

    Hart, Gus L. W.; Nelson, Lance J.; Zhou, Fei; Ozolins, Vidvuds

    2012-10-01

    First-principles codes can nowadays provide hundreds of high-fidelity enthalpies on thousands of alloy systems with a modest investment of a few tens of millions of CPU hours. But a mere database of enthalpies provides only the starting point for uncovering the ``alloy genome.'' What one needs to fundamentally change alloy discovery and design are complete searches over candidate structures (not just hundreds of known experimental phases) and models that can be used to simulate both kinetics and thermodynamics. Despite more than a decade of effort by many groups, developing robust models for these simulations is still a human-time-intensive endeavor. Compressive sensing solves this problem in dramatic fashion by automatically extracting the ``sparse model'' of an alloy in only minutes. This new paradigm to model building has enabled a new framework that will uncover, automatically and in a general way across the periodic table, the important components of such models and reveal the underlying ``genome'' of alloy physics.

  18. Utilization of titanium alloy equipment

    Microsoft Academic Search

    N. M. Shmakov; V. S. Mikheev

    1974-01-01

    Alloys AT-3 and AT-6 have wide application in practice in contrast to many series containing titanium alloyed with cheap obtainable elements such as aluminum, chromium, iron, silicon, and boron. Alloys AT-3 and AT-6 are processable. Extruded electrodes consisting of magnesio-thermic titanium and added alloying elements were fused twice in a vacuum arc furnace in an argon atmosphere. After machining to

  19. TERNARY ALLOY-CONTAINING PLUTONIUM

    Microsoft Academic Search

    Waber

    1960-01-01

    Ternary alloys of uranium and plutonium containing as the third element ; either molybdenum or zirconium are reported. Such alloys are particularly useful ; as reactor fuels in fast breeder reactors. The alloy contains from 2 to 25 at.% ; of molybdenum or zirconium, the balance being a combination of uranium and ; plutonium in the ratio of from 1

  20. ELECTROLESS-PLATED BRAZING ALLOYS

    Microsoft Academic Search

    P. Patriarca; G. M. Slaughter; W. D. Manly

    1957-01-01

    The electroless-plating process deposits an Ni-P brazing alloy that ; exhibits excellent wetability and flowability in conjunction with each high-; temperature alloys as austenitic stainless steels or Inconel when heated above ; the eutectic temperature in a dry hydrogen atmosphere. Complex tubeto-fin heat ; exchanger assemblies can be fabricated by preplating with electroless Ni-P alloy ; and then brazing at

  1. De-alloyed platinum nanoparticles

    DOEpatents

    Strasser, Peter (Houston, TX); Koh, Shirlaine (Houston, TX); Mani, Prasanna (Houston, TX); Ratndeep, Srivastava (Houston, TX)

    2011-08-09

    A method of producing de-alloyed nanoparticles. In an embodiment, the method comprises admixing metal precursors, freeze-drying, annealing, and de-alloying the nanoparticles in situ. Further, in an embodiment de-alloyed nanoparticle formed by the method, wherein the nanoparticle further comprises a core-shell arrangement. The nanoparticle is suitable for electrocatalytic processes and devices.

  2. PLUTONIUM-URANIUM-TITANIUM ALLOYS

    Microsoft Academic Search

    Coffinberry

    1959-01-01

    A plutonium-uranium alloy suitable for use as the fuel element in a fast ; breeder reactor is described. The alloy contains from 15 to 60 at.% titanium ; with the remainder uranium and plutonium in a specific ratio, thereby limiting ; the undesirable zeta phase and rendering the alloy relatively resistant to ; corrosion and giving it the essential characteristic

  3. Boron addition to alloys

    SciTech Connect

    Coad, B. C.

    1985-08-20

    A process for addition of boron to an alloy which involves forming a melt of the alloy and a reactive metal, selected from the group consisting of aluminum, titanium, zirconium and mixtures thereof to the melt, maintaining the resulting reactive mixture in the molten state and reacting the boric oxide with the reactive metal to convert at least a portion of the boric oxide to boron which dissolves in the resulting melt, and to convert at least portion of the reactive metal to the reactive metal oxide, which oxide remains with the resulting melt, and pouring the resulting melt into a gas stream to form a first atomized powder which is subsequently remelted with further addition of boric oxide, re-atomized, and thus reprocessed to convert essentially all the reactive metal to metal oxide to produce a powdered alloy containing specified amounts of boron.

  4. Magnesium and magnesium alloys

    SciTech Connect

    Avedesian, M.; Baker, H. [eds.

    1998-12-31

    This new handbook is the most comprehensive publication of engineering information on commercial magnesium alloys under one cover in the last sixty years. Prepared with the cooperation of the International Magnesium Association, it presents the industrial practices currently used throughout the world, as well as the properties of the products critical to their proper application. Contents include: general characteristics; physical metallurgy; melting, refining, alloying, recycling, and powder production; casting; heat treatment; forging, rolling, and extrusion; semisolid processing; forming; joining; cleaning and finishing; selection, application, and properties of grades and alloys; design considerations; mechanical behavior and wear resistance; fatigue and fracture-mechanics; high-temperature strength and creep; corrosion and stress-corrosion cracking; specification.

  5. Noble alloys in dentistry.

    PubMed

    Gettleman, L

    1991-04-01

    Noble metals used for dental castings continue to consist of alloys of gold, palladium, and silver (not a noble metal), with smaller amounts of iridium, ruthenium, and platinum. The majority are used as a backing for ceramic baking, with the rest used as inlays, onlays, and unveneered crowns. Base metal alloys, principally made of nickel, chromium, and beryllium have gained widespread usage, especially in the United States, due to their lower cost and higher mechanical properties. The current literature, for the most part, cites the use of noble alloys as controls for trials of alternative materials. Direct gold (gold foil) still retains a following and a number of new patents were founded. PMID:1777669

  6. Solvothermal synthesis of gallium-indium-zinc-oxide nanoparticles for electrolyte-gated transistors.

    PubMed

    Santos, Lídia; Nunes, Daniela; Calmeiro, Tomás; Branquinho, Rita; Salgueiro, Daniela; Barquinha, Pedro; Pereira, Luís; Martins, Rodrigo; Fortunato, Elvira

    2015-01-14

    Solution-processed field-effect transistors are strategic building blocks when considering low-cost sustainable flexible electronics. Nevertheless, some challenges (e.g., processing temperature, reliability, reproducibility in large areas, and cost effectiveness) are requirements that must be surpassed in order to achieve high-performance transistors. The present work reports electrolyte-gated transistors using as channel layer gallium-indium-zinc-oxide nanoparticles produced by solvothermal synthesis combined with a solid-state electrolyte based on aqueous dispersions of vinyl acetate stabilized with cellulose derivatives, acrylic acid ester in styrene and lithium perchlorate. The devices fabricated using this approach display a ION/IOFF up to 1 × 10(6), threshold voltage (VTh) of 0.3-1.9 V, and mobility up to 1 cm(2)/(V s), as a function of gallium-indium-zinc-oxide ink formulation and two different annealing temperatures. These results validates the usage of electrolyte-gated transistors as a viable and promising alternative for nanoparticle based semiconductor devices as the electrolyte improves the interface and promotes a more efficient step coverage of the channel layer, reducing the operating voltage when compared with conventional dielectrics gating. Moreover, it is shown that by controlling the applied gate potential, the operation mechanism of the electrolyte-gated transistors can be modified from electric double layer to electrochemical doping. PMID:25517251

  7. ANALYSIS OF THE WATER-SPLITTING CAPABILITIES OF GALLIUM INDIUM PHOSPHIDE NITRIDE (GaInPN)

    SciTech Connect

    Head, J.; Turner, J.

    2007-01-01

    With increasing demand for oil, the fossil fuels used to power society’s vehicles and homes are becoming harder to obtain, creating pollution problems and posing hazard’s to people’s health. Hydrogen, a clean and effi cient energy carrier, is one alternative to fossil fuels. Certain semiconductors are able to harness the energy of solar photons and direct it into water electrolysis in a process known as photoelectrochemical water-splitting. P-type gallium indium phosphide (p-GaInP2) in tandem with GaAs is a semiconductor system that exhibits water-splitting capabilities with a solar-tohydrogen effi ciency of 12.4%. Although this material is effi cient at producing hydrogen through photoelectrolysis it has been shown to be unstable in solution. By introducing nitrogen into this material, there is great potential for enhanced stability. In this study, gallium indium phosphide nitride Ga1-yInyP1-xNx samples were grown using metal-organic chemical vapor deposition in an atmospheric-pressure vertical reactor. Photocurrent spectroscopy determined these materials to have a direct band gap around 2.0eV. Mott-Schottky analysis indicated p-type behavior with variation in fl atband potentials with varied frequencies and pH’s of solutions. Photocurrent onset and illuminated open circuit potential measurements correlated to fl atband potentials determined from previous studies. Durability analysis suggested improved stability over the GaInP2 system.

  8. Studies on the effect of ammonia flow rate induced defects in gallium nitride grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Suresh, S.; Lourdudoss, S.; Landgren, G.; Baskar, K.

    2010-10-01

    Gallium nitride (GaN) epitaxial layers were grown with different V/III ratios by varying the ammonia (NH 3) flow rate, keeping the flow rate of the other precursor, trimethylgallium (TMG), constant, in an MOCVD system. X-ray rocking curve widths of a (1 0 2) reflection increase with an increase in V/III ratio while the (0 0 2) rocking curve widths decrease. The dislocation density was found to increase with an increase in ammonia flow rate, as determined by hot-wet chemical etching and atomic force microscopy. 77 K photoluminescence studies show near band emission at 3.49 eV and yellow luminescence peaking at 2.2 eV. The yellow luminescence (YL) intensity decreases with an increase in V/III ratio. Positron annihilation spectroscopy studies show that the concentration of Ga-like vacancies increases with an increase in ammonia flow rate. This study confirms that the yellow luminescence in the GaN arises due to deep levels formed by gallium vacancies decorated with oxygen atoms.

  9. Temperature effects on luminescence properties of Cr3+ ions in alkali gallium silicate nanostructured media

    NASA Astrophysics Data System (ADS)

    Lipinska-Kalita, Kristina E.; Krol, Denise M.; Hemley, Russell J.; Kalita, Patricia E.; Gobin, Cedric L.; Ohki, Yoshimichi

    2005-09-01

    We have investigated the optical properties of Cr3+ ions in an alkali gallium silicate glass system and in two glass-based nanocomposites with nucleated ?-Ga2O3 nanocrystals. The nucleation and growth of the nanocrystalline phase in the host glass matrix were monitored by Raman scattering spectroscopy and angle-dispersive x-ray diffraction. A broadband luminescence, associated with the 4T2-4A2 transition from the weak crystal field of octahedral Cr3+ sites, dominated the emission of the precursor as-quenched glass. The luminescence spectra of the synthesized glass-ceramic nanocomposites revealed a crystal-like 2E-4A2 strong emission and indicated that the major fraction of Cr3+ ions was located within the nanocrystalline environment. The variable-temperature studies of the nanocomposites demonstrated that the fluorescence of Cr3+ ions can be transformed from sharp R lines of the 2E-4A2 transition to a combination of R lines and of the broad band of the 4T2-4A2 transition. We propose a simple distribution model where the major part of Cr3+ ions is located in the nanocrystalline phase of the glass-ceramic composites in the octahedral environment, substituting the gallium atoms in the ?-Ga2O3 crystal structure. The developed nanocrystalline glass-ceramics are a promising class of Cr3+-doped oxide glass-based optically active composite materials.

  10. Potential aluminium(III)- and gallium(III)-selective optical sensors based on porphyrazines.

    PubMed

    Goslinski, Tomasz; Tykarska, Ewa; Kryjewski, Michal; Osmalek, Tomasz; Sobiak, Stanislaw; Gdaniec, Maria; Dutkiewicz, Zbigniew; Mielcarek, Jadwiga

    2011-01-01

    Porphyrazines possessing non-coordinating alkyl (propyl) and aralkyl (4-tert-butylphenyl) groups in the periphery were studied as optical sensors for a set of mono-, di- and trivalent cations. Investigated porphyrazines in the UV-Vis monitored titrations revealed significant responses towards aluminium and gallium cations, unlike other metal ions studied. Additionally, porphyrazine possessing 4-tert-butylphenyl peripheral substituents showed sensor property towards ruthenium cation and was chosen for further investigation. The presence of isosbestic points in absorption spectra for its titration with aluminium, gallium and ruthenium cations, accompanied by a linear Benesi-Hildebrand plot, proved complex formation. The continuous variation method was used to determine binding stoichiometry in 1:1 porphyrazine-metal ratio. X-Ray studies and density functional theory calculations were employed to investigate octa(4-tert-butylphenyl)porphyrazine structure. The results helped to explain the observed selectivity towards certain ions. Interaction between ion and porphyrazine meso nitrogen in a Lewis acid-Lewis base manner is proposed. PMID:21558658

  11. Sensitivity of chest radiography, computed tomography, and gallium scanning to metastasis of lung carcinoma

    SciTech Connect

    Friedman, P.J.; Feigin, D.S.; Liston, S.E.; Alazraki, N.P.; Haghighi, P.; Young, J.A.; Peters, R.M.

    1984-10-01

    To determine the efficacy of radiologic techniques in preoperative staging of the mediastinum for lung carcinoma, the authors studied 45 patients with chest films supplemented with oblique views, esophagrams, gallium scans, and computed tomograms (CT). They interpreted the studies and correlated surgical findings using a modified classification of lymph node regions. The mediastinum was positive on chest films in 14 of the 21 cases with pathologically proved mediastinal metastases (33% false-negative). Gallium scans in cases with a positive primary were positive in 12 of 15 cases with mediastinal or hilar metastases (20% false-negative). Computed tomography showed nodes over 1 or 1.5 cm in size in or adjacent to the biopsy-positive node region in 18 of 19 patients (5% false-negative), extranodal mediastinal involvement, and 9 of 10 proven hilar metastases. Computed tomography is a sensitive screening technique in patients who would otherwise require an invasive staging procedure, but is not highly specific (false-positive rate 38%).

  12. Dispersion and coalescence of oil droplets by ultrasound and application for solvent extraction of gallium

    NASA Astrophysics Data System (ADS)

    Yasuda, Keiji; Thanh Nguyen, Tam; Okura, Risa; Nakayama, Shingo; Asakura, Yoshiyuki; Jin, Jiye

    2015-07-01

    To improve the performance of solvent extraction of rare metals, the effects of ultrasonic and organic solvent conditions on the demulsification of emulsions were examined. Optimized conditions were adopted in the solvent extraction of gallium by ultrasonic irradiation. As organic solvents, chloroform, 1,2-dichloromethane, p-bromotoluene, bromobenzene, and 1,2-dibromoethane were employed. Emulsification was carried out using a horn-type transducer at 20 kHz. Demulsification was performed with plate-type transducers at 1.0–4.8 MHz. The demulsification time decreased with increasing ultrasonic frequency and power because the primary and secondary acoustic forces of droplets become stronger. Inclining the vessel shortened the demulsification time. In the case of chloroform at a low solution pH, the demulsification time was shortest since the zeta potential of droplets was close to zero. The sequential ultrasonic irradiation at 20 kHz and 4.8 MHz greatly shortens the operation time needed for solvent extraction of gallium from an aqueous solution.

  13. Optical properties of gallium oxide clusters from first-principles calculations.

    PubMed

    Rahane, Amol B; Deshpande, Mrinalini D; Chakraborty, Sudip

    2012-11-01

    The optical properties of the (Ga(2)O(3))(n) clusters, with n = 1-10, have been studied within the framework of time dependent density functional theory. The gallium oxide cluster geometries showed evolution from planar configuration (C(2v)) for Ga(2)O(3) to layered globular configuration (C(s)) for (Ga(2)O(3))(10) via corundum configuration (D(3d)) for (Ga(2)O(3))(4). For n ? 5, with the increase in coordination of Ga and O atoms, the polarizability decreases with the size of the cluster. For n ? 6, with the stabilization of average coordination number for gallium and oxygen atoms, the decrease in polarizability is very small. Further, the optical absorption spectra and the corresponding optical gap have been calculated. The overall shape of the calculated spectra strongly depend on cluster geometries. With the increase in size, the discrete spectra of small clusters evolves into quasicontinuous spectra. For n = 10, the spectra show a smooth absorption edge that is a characteristic of the bulk. It is observed that the optical gap oscillate with an increase in the cluster size. The calculated optical gap of these clusters are lower than the band gap of ?- and ?-Ga(2)O(3) phases. The underestimation of the calculated values of the cluster optical gap is due to the use of local density approximation. PMID:23043515

  14. Bronchoalveolar lavage and gallium-67 lung scanning in the evaluation of asbestos-exposed individuals

    SciTech Connect

    Al-Tawil, W.G.

    1986-01-01

    In this study, an attempt is made to evaluate certain parameters that might indicate the beginning of a certain fibrogenic activity in the lung parenchyma, even before such changes become visible on the chest x-ray. The hypothesis is that studies such as certain bronchoalveolar immunological characteristics and Gallium-67 lung scans may be more sensitive indicators of parenchymal lung damage in response to asbestos inhalation than conventional radiographic criteria. If so, then in those cases where the criteria for the diagnosis of asbestosis lack the presence of parenchymal changes, it would be unwise to deny the diagnosis unless further investigation, such as the bronchoalveolar lavage fluid analysis and the Gallium-67 lung scan techniques, are made available. The most significant laboratory parameter for bronchoalveolar lavage, in this study, is that of Neutrophils (PMNs). All three asbestos-exposed groups showed no differences when compared with each other, while such differences were statistically significant when such groups were separately compared with the normal comparison group. A similar finding existed also when the Helper: suppressor T-Cell ratios were compared, and found to be higher in all the asbestos-exposed groups.

  15. Differential uptake of gallium-67-labeled liposomes between tumors and inflammatory lesions in rats

    SciTech Connect

    Ogihara, I.; Kojima, S.; Jay, M.

    1986-08-01

    The differential gallium-67 (/sup 67/Ga) accumulation in tumors and inflammatory lesions in rats after i.v. injection of liposome encapsulated /sup 67/Ga ((/sup 67/Ga)liposomes) was studied. The /sup 67/Ga accumulation in the tumor was much greater than that in the granulation tissue regardless of the surface charge of liposomes; however, the difference between the two tissues was the greatest when using positive charged liposomes. Gallium-67 delivery to tumors by liposomes was greater than that to granulation tissue in all stages of growth. After i.v. injection, the accumulation of /sup 67/Ga in the tumor reached a maximum at 12 hr, whereas in the granulation tissue it was delayed to 24 hr postinjection. In the study of tissue distribution of /sup 67/Ga in rats bearing both tumor and granulation tissue, positively charged liposomes preferentially delivered /sup 67/Ga to the tumor than to the granulation tissue. These results suggest that (/sup 67/Ga)liposomes are able to discriminate between the tumor and the inflammatory lesion.

  16. Preparation of gallium-68 radiopharmaceuticals for positron tomography. Progress report, November 1, 1977-October 31, 1980

    SciTech Connect

    Welch, M.J.

    1980-06-01

    Although the germanium-68 ..-->.. gallium-68 generator is probably the only source of positron-emitting radionuclides that could enable the widespread application of positron tomography, the commercially available /sup 68/Ga//sup 68/Ge generator system suffers from several major disadvantages. The most important of these is that the generator is eluted with EDTA, which forms a very strong chelate with gallium. In order to produce radiopharmaceuticals other than /sup 68/Ga-EDTA, it is first necessary to break the stable EDTA complex and remove all traces of EDTA. This procedure adds several steps and a significant amount of time to procedures for preparing /sup 68/Ga-radiopharmaceuticals. We have developed a new generator using a solvent extraction system which will produce /sup 68/Ga-oxine (8-hydroxyquinoline), a weak chelate. Using this agent we have synthesized several /sup 68/Ga-radiopharmaceuticals and tested them in vitro and in vivo. We have also carried out some preliminary studies to compare generator systems which produce /sup 68/Ga in an ionic form. Attempts have been made using polarographic and chromatographic techniques, and in vivo distribution data to investigate the stability of radiogallium complexes with a series of potentially lipophilic complexing agents.

  17. Synthesis of Gallium-oxide nanoparticles and nanowires by using a thermal plasma

    NASA Astrophysics Data System (ADS)

    Kim, Tae-Hee; Park, Dong-Wha; Choi, Sooseok

    2015-04-01

    Gallium-oxide (Ga2O3) nanoparticles and nanowires were synthesized using a direct current arc thermal plasma. Gallium nitrate hydrate (Ga(NO3)3·xH2O) was used as a raw material for the synthesis of the Ga2O3 nanomaterials. (Ga(NO3)3·xH2O) was injected into the area of the thermal plasma in a liquid state with two different solvents, distilled water (H2O) and methyl alcohol (CH3OH). The as-synthesized Ga2O3 nanomaterials were characterized according to their crystallinity and morphology. In the cases of both the H2O and CH3OH solvents, the crystalline monoclinic ?-Ga2O3 nanomaterials were synthesized in a reaction tube. Amorphous Ga2O3 nanoparticles were collected in a chamber in the case of the H2O solvent whereas amorphous Ga2O3 nanowires were found in the case of the CH3OH solvent. As a result, ?-Ga2O3 nanoparticles, amorphous nanoparticles and nanowires were selectively synthesized by using a thermal plasma process, depending on the collection position of the product and the type of mixing solution.

  18. Chemical exfoliation and optical characterization of threading-dislocation-free gallium-nitride ultrathin nanomembranes

    NASA Astrophysics Data System (ADS)

    ElAfandy, Rami T.; Majid, Mohammed A.; Ng, Tien Khee; Zhao, Lan; Cha, Dongkyu; Ooi, Boon S.

    2014-11-01

    Semiconductor nanostructures have generated tremendous scientific interests as well as practical applications stemming from the engineering of low dimensional physics phenomena. Unlike 0D and 1D nanostructures, such as quantum dots and nanowires, respectively, 2D structures, such as nanomembranes, are unrivalled in their scalability for high yield manufacture and are less challenging in handling with the current transfer techniques. Furthermore, due to their planar geometry, nanomembranes are compatible with the current complementary metal oxide semiconductor (CMOS) technology. Due to these superior characteristics, there are currently different techniques in exfoliating nanomembranes with different crystallinities, thicknesses and compositions. In this work we demonstrate a new facile technique of exfoliating gallium nitride (GaN) nanomembranes with novel features, namely with the non-radiative cores of their threading-dislocations (TDs) being etched away. The exfoliation process is based on engineering the gallium vacancy (VGa) density during the GaN epitaxial growth with subsequent preferential etching. Based on scanning and transmission electron microscopies, as well as micro-photoluminescence measurements, a model is proposed to uncover the physical processes underlying the formation of the nanomembranes. Raman measurements are also performed to reveal the internal strain within the nanomembranes. After transferring these freely suspended 25 nm thin GaN nanomembranes to other substrates, we demonstrate the temperature dependence of their bandgap by photoluminescence technique, in order to shed light on the internal carrier dynamics.

  19. Characterization of the Absolute Crystal Polarity across Twin Boundaries in Gallium Phosphide Using Convergent-Beam Electron Diffraction

    Microsoft Academic Search

    Dov Cohen; Stuart McKernan; C. Barry Carter

    1999-01-01

    The measurement of absolute crystal polarity is crucial to understanding the structural properties of many planar defects in compound semiconductors. Grain boundaries, including twin boundaries, in the sphalerite lattice are uniquely characterized by the crystallographic misorientation of individual grains and the direction of the crystal polarity in domains adjoining the grain boundary. To evaluate crystal polarity in gallium phosphide (GaP),

  20. Interaction of the anticancer gallium(III) complexes of 8-hydroxyquinoline and maltol with human serum proteins.

    PubMed

    Enyedy, Éva A; Dömötör, Orsolya; Bali, Krisztina; Hetényi, Anasztázia; Tuccinardi, Tiziano; Keppler, Bernhard K

    2015-01-01

    Tris(8-quinolinolato)gallium(III) (KP46) and tris(maltolato)gallium(III) (GaM) are promising orally active antitumor metallodrugs currently undergoing clinical trials. Their interaction with human serum albumin (HSA) and transferrin (Tf) was studied in detail in aqueous solution by the combination of various methods such as spectrofluorometry, UV-vis spectrophotometry, (1)H and saturation transfer difference NMR spectroscopy, and ultrafiltration-UV-vis spectrophotometry. Binding data were evaluated quantitatively. Tf was found to replace the original ligand much less efficiently in KP46 than in GaM, whereas a significant noncovalent binding of KP46 with HSA (log K' = 4.04) retaining the coordination environment around gallium(III) was found. The interaction between HSA and KP46 was also confirmed by protein-complex modeling calculations. On the basis of the conditional stability constants, the distribution of gallium(III) in serum was computed and compared for these metallodrugs under physiological conditions, and revealed the prominent role of HSA in the case of KP46 and that of Tf for GaM. PMID:25398250